Holosun 507C vs 507K: Which Red Dot Fits Your Pistol?

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The Short Answer

If you're trying to decide between the Holosun 507C and the 507K, the decision usually comes down to your slide, not the optic itself. The 507C X2 uses the RMR footprint, which makes it the natural fit for compact and full-size pistols like the Glock 19 and Glock 17 (assuming your slide is cut or plated for RMR). The 507K X2 uses the smaller K footprint, built for slimline and micro-compact slides where an RMR-size housing simply won't sit flush or fit the available screw pattern. Both optics share the same core reticle system — a 2 MOA dot, a 32 MOA circle, or both together — so the shooting experience is nearly identical once you've picked the one that actually mounts to your gun.

Side-by-Side Spec Table

Specs are drawn from Holosun's 507C X2 and 507K X2 product pages. For current street pricing, see our current Holosun prices page.

Footprint and Which Pistols Each Fits

The 507C's RMR footprint is one of the most widely supported cuts on the market, so it generally lines up with factory optic cuts or aftermarket plates on compact and full-size pistols. The 507K's K footprint was built for smaller carry guns and typically pairs with RMSc-style cuts found on micro-compact slides. These are general patterns, not guarantees — optic cuts vary by manufacturer and even by generation within the same pistol line. Always verify your specific slide's cut or plate compatibility before buying, and mount any optic using the manufacturer's plates and instructions, or have a qualified gunsmith do it. Never mill a slide yourself, and always confirm the firearm is unloaded before you start working on it.

Window Size and Sight Picture

Window dimensions are one of the more practical differences between these two optics. The 507C's window measures 0.91 x 0.63 in, giving it a slightly larger viewing area suited to the bigger housing it rides in. The 507K's window is listed by Holosun at 0.58 x 0.77 in. On a micro-compact pistol with a shorter sight radius, the 507K's smaller housing keeps the optic from overwhelming the slide, while the 507C's larger window can feel more open on a duty-size gun. Neither window size is objectively better — it's a tradeoff that lines up with the footprint decision you've already made.

Battery and Power Features

Both optics run on a single CR1632 battery loaded through a side tray, so you never have to remove the optic (and lose zero) to swap batteries. Holosun lists battery life up to 50,000 hours on both models, and both include Shake Awake to power the dot on when the gun moves. The meaningful difference is solar: the 507C X2 has a solar failsafe panel on top of the housing, while the 507K X2 does not. On a duty or range gun that sits exposed to light, solar is a nice backstop; on a concealed-carry K-footprint gun, the smaller housing trades that feature away for compactness.

What About the New 507C X3?

Holosun introduced the 507C X3 at SHOT Show 2026 as an update to the RMR-footprint line, detailed in the launch release from The Outdoor Wire. It keeps the RMR footprint, bumps the window slightly to 0.91 x 0.67 in, still runs on a CR1632 in a side tray, and extends battery life up to 100,000 hours while shaving weight to 1.55 oz. Holosun lists it at $352.93. As of this writing, there's no 507K X3 — the K-footprint line remains on the X2 generation.

Price (Checked Nov 1, 2026)

At list price, the 507C X2 runs $364.69 and the 507K X2 runs $348.22 directly from Holosun. Street pricing moves around more: Primary Arms had the 507C X2 at $232.99 and the 507K X2 at $295.99 on Nov 1, 2026. Check our current Holosun prices page for the latest numbers before you buy.

FAQ

Will a 507K fit a Glock 19? Not directly. Glock's own optic-mounting resources don't list a G19 plate for the K footprint, so the 507K isn't a standard fit for that slide. Check Glock's optic mounting page for current plate options.

Is the 507C too big for a P365? It can be. The P365 family generally uses smaller optic cuts than RMR, so check your specific model and available plates before assuming a 507C will fit.

Does the 507K have solar? No. Only the 507C X2 (and the newer 507C X3) include a solar failsafe panel.

What battery does the 507C use? A single CR1632, loaded through a side tray without removing the optic from the slide.

For more on dot sizing and setup once you've picked an optic, see our guides on 3 MOA vs 6 MOA red dots and how to zero a red dot in five steps.