Holosun 407K vs 507K, and how the K body differs from the C

By the OpticVerdict Editorial Team.
Research-based roundup · Updated 2026-07-26

Holosun's naming tells you two separate things at once and buyers usually only decode one of them. The number, 407 or 507, is the reticle. The letter, K or C, is the body and the footprint. Get the letter wrong and the optic does not fit your pistol at all, which is why we start there.

How these picks were made: a research-based roundup built from OpticsPlanet's spec tables for all six optics in the family, prices and stock read from each variant's own listing rather than from a headline figure, and the owner records on the carded listings, which run to 461 ratings on the 507C, 250 on the green 507K, 200 on the 407K and 144 on the 407C. Scores are our editorial opinion, not a hands-on test. Where the retailer's own page contradicts itself we say so rather than pick the flattering number. See how we evaluate.

Start with the letter, not the number

In Holosun's pistol line the number is the reticle and the letter is the body. A 407 gives you a single dot. A 507 gives you the Multi-Reticle System, so you can run a 2 MOA dot, a 32 MOA circle, or both together. That is the whole of it, and if the reticle question is what brought you here we have already answered it in detail on our Holosun 407C vs 507C comparison.

This page is about choosing between them. If you have already chosen and want the depth on one optic, we review each of these individually: the HS407K-X2, the 507K in red and green, and the HS407C-X2.

The letter is the part that decides whether you can buy the optic at all. C is the full-size body on an RMR footprint, which is what most full-size and compact slides are cut for. K is the sub-compact body on Holosun's K footprint, an RMS or RMSc-class pattern, made for carry pistols like the SIG P365 family and the Glock 43X. They are not interchangeable. Choosing the reticle before you have checked the footprint is choosing the wrong thing first.

All six optics, side by side

Every figure below is from Holosun's specifications as published by the retailer, with prices and stock read from each variant's own listing on July 26, 2026.

Read down the price column and the pattern is the opposite of the one buyers expect. The largest optic is the cheapest. Every step you take toward a smaller body or a busier reticle costs money: the K footprint adds $39 over the full-size C, green adds $15 to $24, and the circle-dot reticle adds $71. A green circle-dot K optic ends up at $319.99, which is $134 more than a full-size red dot-only C at $185.99, for the same brand and the same generation.

507C vs 507K: the same reticle in two different bodies

The 407K versus 407C question above has a twin, and it is the cleaner experiment of the two. The HS507C-X2 and the HS507K X2 carry the identical reticle, Holosun's Multi-Reticle System with a 2 MOA dot, a 32 MOA circle, or both together. Nothing about the aiming picture changes between them. Only the body does: the 507C is the full-size C on the RMR footprint at 1.5 oz, and the 507K is the sub-compact K on the RMS/RMSc-class footprint at 1 oz.

So 507C vs 507K isolates the price of the footprint with nothing else moving, and the answer is blunt: the smaller optic costs $63 more. The 507C also brings Solar Failsafe, which keeps the reticle lit from ambient light if the battery dies and which neither K optic lists, and it does it while being the cheaper of the two. Put the other way round, 507K vs 507C is a trade of half an ounce and a slide that will actually take the optic, paid for with $63, a smaller window and the loss of the solar panel.

That makes the decision the same one this whole page argues: start with the slide. If your pistol is cut for an RMR pattern, the 507C is the better optic and the cheaper one, and there is no case for the 507K. If you carry a sub-compact whose slide will not take a C body, the 507K is the only one of the two that mounts, and the premium is the cost of the footprint rather than a better sight. Choosing between the reticles instead of the bodies is a different question, and our 407C vs 507C comparison is the page for it.

What the extra money does not buy. Moving from the C to the K does not get you a better optic. The C has the larger window, the finer 2 MOA dot, 50 MOA of adjustment and Solar Failsafe, which keeps the reticle running from light if the battery dies and which neither K optic lists. What the K gets you is 0.5 oz less weight and, decisively, a footprint that fits a carry slide.

Best K-series overall: Holosun HS407K-X2 Sub-Compact Red Dot Sight

4.5/5 our editorial score

4.8/5 from 200 ratings on OpticsPlanet, 198 of them written

1x · 0.58 x 0.77 in window · 6 MOA dot · open emitter · RMS/RMSc K footprint · 12 brightness settings with 2 night-vision levels · Shake Awake · side-tray CR1632 rated 50,000 hours · IP67 · 1 oz

around $220 exact price on OpticsPlanet

Check price on OpticsPlanet

Read the full review →

This is the K to buy for most carry pistols, and the reason is a piece of hardware rather than the reticle: the battery sits in a tray on the SIDE of the housing, so you change it without unmounting the optic and without losing your zero. Owners rate that above every other feature, and the most helpful review on the listing is from a shooter who owns both this and the 507K and prefers this one outright, partly for the battery tray and partly because he wants a plain dot rather than a circle. The 6 MOA dot is the other half of the argument: on a carry gun at conversational distance you want the dot found fast, and 6 MOA is three times the area of the 2 MOA dot on the full-size 407C. There is also an unusually consistent thread of astigmatic shooters saying this dot is cleaner than others they have tried, one describing it as the clearest of at least five brands with only slight blurring. Two things to settle before you buy. Check your slide, because the K footprint is not a universal RMSc and some pistols need an adapter plate. And put a dab of thread locker on the battery-tray screw, for the reason in the cons below.

Pros

• The side battery tray is the standout: swap the CR1632 without taking the optic off the slide, which means no re-zero. Owners repeatedly name this as the reason they chose it over the 507K
• A 6 MOA dot is the right size for a carry gun, roughly three times the area of the 2 MOA dot on the full-size 407C and much faster to pick up under stress
• The deepest owner record in the K series at 198 written reviews and 4.8 out of 5, and a recurring thread of astigmatic shooters calling the dot unusually clean
• Genuinely rugged for a 1 oz optic: 7075-T6 aluminium, IP67, a 5000G vibration rating, Shake Awake and a 50,000 hour battery life
• The cheapest way into the K body, and available with a green dot as the HE407K-GR X2 for $239.99 if green suits your eyes better

Cons

• Apply thread locker to the battery-tray screw before you carry it. Two separate owners report the screw backing out under recoil and the tray, battery and screw leaving the gun mid-drill. Both fixed it with thread locker, which makes this a known and cheap fix rather than a reason to avoid the optic
• A minority but repeated zero-retention problem: several owners describe a unit that would not hold zero, one seeing groups open from 4 to 5 inches out to roughly two feet at 7 yards, and an exchanged second unit doing the same. Many more owners report no issue at all, so treat it as a reason to confirm your zero early rather than as the normal experience
• The K footprint is not a true RMSc on every pistol. One owner says so plainly, and others report needing an adapter plate or pin fitting; one could not get enough down elevation to zero at 10 yards. Check your specific slide, and check whether the plate is an extra cost
• The small window takes some learning. A 0.58 by 0.77 inch view is less forgiving than a full-size optic and new red dot shooters report a find-the-dot period
• A single 6 MOA dot is all you get, with no circle option on this model. That is the design, not a fault, but if you want the circle you are looking at the 507K below

Best for: a concealed-carry pistol where the slide takes a K or RMSc-class optic and you want the simplest, fastest aiming point with the easiest battery changes. Step up to the 507K if you want the circle around the dot, or drop to the full-size 407C if your slide is cut for an RMR footprint.

Key specifications

Manufacturer	Holosun
Window size	0.58 x 0.77 in
Reticle	6 MOA dot
Emitter type	Open
Footprint	RMS / RMSc class (Holosun K)
Brightness settings	12 (10 daylight, 2 night-vision compatible)
Battery	CR1632 in a side tray, up to 50,000 hours
Adjustment	1 MOA clicks
Housing	7075-T6 aluminium, anodised
Sealing and shock	IP67, 5000G vibration rating
Dimensions and weight	1.6 x 0.98 x 0.95 in, 1 oz
In the box	Optic, multi tool, lens cloth, manual
Model carded	HS407K X2 red (of 4 listed variants; 2 factory demo units excluded, green HE407K-GR X2 available at $239.99)

“The only one that will not need to be removed from the firearm to load a new battery... far superior to the 507k. Go with this 6MOA dot.”

Sig Powers, verified owner via OpticsPlanet, 16 of 22 readers found it helpful

Best K-series if you want the circle: Holosun HE507K-GR X2 Green Dot Reflex Sight

4.4/5 our editorial score

4.7/5 from 250 ratings on OpticsPlanet

1x · 0.58 x 0.77 in window · green Multi-Reticle System, circle dot / 2 MOA dot / 32 MOA circle · open emitter · K footprint · 12 brightness settings with 2 night-vision levels · Lock Mode · Shake Awake · side-tray CR1632 rated 50,000 hours · IP67 · 1 oz

around $320 exact price on OpticsPlanet

Check price on OpticsPlanet

Read the full review →

Same body, same footprint, same weight, same side battery tray as the 407K above. What you are paying the extra $95 for is the reticle system and the colour. The Multi-Reticle System gives you three choices you can cycle through: a 2 MOA dot on its own for precision, a 32 MOA circle on its own, or both together, and the circle is what makes the optic quick to find when you present the gun in a hurry. This green version carries by far the deepest owner record in the entire K family at 250 ratings, roughly three times the red 507K, which is worth knowing because green and red are not equally easy for every pair of eyes to see. It also adds Lock Mode, which stops the buttons changing your settings in a holster. If you want this reticle in red instead, the HS507K X2 is the same optic at $295.99 and saves you $24, though it has a much thinner review record at 89.

Pros

• The Multi-Reticle System is the real upgrade over the 407K: 2 MOA dot alone, 32 MOA circle alone, or circle-dot together, switchable on the gun
• The deepest owner record of any optic in this comparison at 250 ratings and 4.7 out of 5
• Keeps everything that makes the 407K work: the same 1 oz K-footprint body, the same side battery tray with no-unmount battery changes, Shake Awake and a 50,000 hour rating
• Lock Mode prevents accidental button presses and setting changes, which matters on an optic that spends its life in a holster
• Reported by owners as a direct fit on several popular carry slides without a plate, including the SIG P365X, P365XL and P365 XMacro and the Canik MC9

Cons

• It is the most expensive optic here at $319.99, which is $95 over the 407K for a reticle change and a colour. The red HS507K X2 at $295.99 narrows that gap by $24 if green is not the point for you
• Every K-body caveat still applies, because it is the same body: check your slide against the K footprint, and put thread locker on the battery-tray screw
• Slides with a four-boss interface need an adapter plate, which OpticsPlanet states on the listing. Budget for it, or confirm your pistol is a direct fit first
• A 32 MOA circle inside a 0.58 by 0.77 inch window is a lot of reticle in a small view, and at least one owner of the 407K chose the plain dot specifically because he finds the circle distracting

Best for: the carry shooter who wants the circle-dot to speed up target acquisition and finds a green reticle easier to see than red. Take the 407K instead if you prefer an uncluttered dot or want to save $95, and take the red HS507K X2 if you want this reticle without paying the green premium.

Key specifications

Manufacturer	Holosun
Window size	0.58 x 0.77 in
Reticle	Green MRS: circle dot, 2 MOA dot, or 32 MOA circle
Emitter type	Open
Footprint	RMS class (Holosun K)
Brightness settings	12 (10 daylight, 2 night-vision compatible)
Battery	CR1632 in a side tray, up to 50,000 hours at setting 6
Adjustment	1 MOA clicks
Extras	Lock Mode, Shake Awake, multilayer reflective coatings
Sealing	IP67
Weight	1 oz
Model carded	HE507K-GR X2 (of 4 listed variants; 2 used or demo units excluded, an ACSS Vulcan reticle version also listed)

“Fits perfectly on my P365 xmacro without the need for adapter plate. Love the larger ACSS Vulcan circle dot system - makes it natural and faster to find the dot when aiming quickly.”

A verified owner via OpticsPlanet, writing about the ACSS Vulcan version of this listing

Cheaper, if your slide takes it: Holosun HS407C-X2 Open Reflex Red Dot Sight

4.4/5 our editorial score

4.8/5 from 144 ratings on OpticsPlanet

1x · 0.63 x 0.91 in window · 2 MOA dot · open emitter · RMR footprint · Solar Failsafe · Shake Awake · CR1632 rated 50,000 hours · 50 MOA of adjustment · IP67 · 1.5 oz

around $190 exact price on OpticsPlanet

Check price on OpticsPlanet

Read the full review →

This is the optic that makes the whole comparison worth writing, because it is bigger, has a larger window, adds a solar panel that runs the dot if the battery dies, and costs $39 LESS than the 407K. Nothing about that is intuitive. The catch, and it is the whole reason the K series exists, is the footprint: this is an RMR-pattern optic, which is what full-size and compact slides are usually cut for, and it is not what sub-compact carry pistols like the P365 or the Glock 43X take. So the honest way to choose is to start at your slide rather than at the spec sheet. If your pistol is cut for an RMR footprint, this is the better buy on almost every measure: a bigger view, a finer 2 MOA dot for precision, solar backup, and less money. If your pistol is a sub-compact, this optic is simply not an option and the K premium is the price of admission.

Pros

• Cheapest optic here at $185.99 while having the largest window at 0.63 by 0.91 inches, which is the opposite of what buyers expect
• Solar Failsafe runs the reticle from light if the battery dies, a genuine reliability feature that neither K-series optic on this page lists
• A 2 MOA dot covers about a third of the area of the 407K's 6 MOA dot, so it is the better choice if precision past close range matters to you
• 50 MOA of total windage and elevation adjustment, Shake Awake, a 50,000 hour battery and IP67 sealing
• A strong owner record at 4.8 out of 5 from 144 ratings

Cons

• The RMR footprint is the catch: it will not fit the sub-compact carry slides the K-series optics are made for, so for many buyers this is not a real alternative at any price
• Heavier at 1.5 oz against 1 oz for both K optics, which is 50 percent more weight on a pistol slide
• A 2 MOA dot is more precise but slower to find under stress than the 407K's 6 MOA dot, which is a real trade for a defensive gun
• OpticsPlanet's own page contradicts itself on brightness, with the spec table listing 10 settings and the description saying 12. We use the spec table figure and would not build a decision on it
• Only 4 units were in stock when we checked, so this price and availability are worth confirming before you plan around them

Best for: a full-size or compact pistol already cut for an RMR footprint, where you want a bigger window, a finer dot and solar backup for less money. It is not an option for sub-compact carry slides, which is exactly why the K series costs more.

Key specifications

Manufacturer	Holosun
Window size	0.63 x 0.91 in
Reticle	2 MOA dot
Emitter type	Open
Footprint	RMR
Brightness settings	10 (spec table; the page description says 12)
Battery	CR1632, up to 50,000 hours, plus Solar Failsafe
Adjustment	1 MOA clicks, 50 MOA total windage and elevation
Housing	Aluminium, anodised
Sealing	IP67
Weight	1.5 oz
Model carded	HS407C X2 (of 4 listed variants; an OpticGard cover kit and 2 demo units excluded)

Fitment: what the K footprint actually fits

This is where buyers lose money, so here is what the record actually supports rather than what the marketing implies.

Holosun's K footprint is described as RMS or RMSc class, and for many carry pistols it is a direct mount. The retailer states on the 507K listing that it is a direct fit for the SIG P365X and P365XL, and that slides with a four-boss interface require an adapter plate. Owners confirm direct fits on the P365 XMacro and the Canik MC9, one noting he mounted it to the slide with no plates needed.

But it is not a universal RMSc, and one owner says exactly that. Others report needing an adapter plate or a pin fitting, and one owner could not get enough down elevation to zero his at 10 yards on his pistol. None of that makes the optic bad; it makes the check mandatory. Confirm your exact slide cut before you order, and price the adapter plate if you need one, because a plate can erase the difference between a K optic and the cheaper full-size C.

The battery tray, and the screw you should thread-lock

The single most praised feature across the K series is not the reticle, it is the battery. The CR1632 sits in a tray on the side of the housing, so you change it without taking the optic off the slide and without losing your zero. On an optic that is otherwise fiddly to remount, that is worth real money, and the most helpful review on the 407K listing is built entirely around it.

There is a known catch that owners solved themselves and that we would act on before carrying one. Two separate owners report the battery-tray screw backing out under recoil, with the tray, the battery and the screw leaving the pistol in the middle of a drill. Both fixed it permanently with a dab of thread locker on that screw. It costs almost nothing and takes a minute, and given that this is a carry optic we would treat it as part of the install rather than as a repair.

For what it is worth in context: both K optics are rated to 50,000 hours with Shake Awake enabled, so battery changes are rare events. That is precisely why a screw that quietly loosens over years of recoil is worth pre-empting rather than discovering.

Frequently asked questions

More: Holosun 407C vs 507C · best pistol red dots · best red dot for the SIG P365 · Defender-CCW vs HS407K-X2 · what MOA dot size means.