We Mapped 134 Optics to 11 Footprints. Here Is What We Found.

We built CaliberAPI to answer one question without guessing: does this optic actually fit this pistol? So every optic, every slide, and every fit in the set carries a source link, and we do not publish a fit we cannot cite. The count came out to 134 optics, 11 footprints, and 196 optic-ready pistols. Then we turned the data on itself and counted. The short version is that the optic market and the pistol market care about two different footprints, and one brand makes almost half of all the optics.

Here is what the map looks like once it is finished.

Which footprint do the most pistols use?

The RMSc, by a wide margin. 80 of the 196 pistols in the set are cut for it. That is 41 percent of every optic-ready pistol in the set. The next most common cut is the Holosun K at 26 pistols, then the Glock MOS plate system at 16, and the Walther PDP 2.0 at 10. After that everything is in single digits.

So if you bought a sub-compact carry gun in the last few years, the math says your slide is probably RMSc. That one cut covers more pistols than the other ten footprints combined.

Which footprint do the most optics use?

Now ask it the other way. The RMR has 47 optics built for it, more than any other footprint in the set. The RMSc is second at 32. Then it falls off a cliff: DeltaPoint Pro at 16, Holosun EPS at 9, the Holosun K and Holosun 509T at 8 each, Docter at 6, ACRO at 5.

The RMR result is the one we did not expect. It has the most optics and nearly the fewest pistols. 47 optics fight over a cut that only 7 pistols in the data are milled for. The RMSc is the exact mirror: fewer optics, far more guns. Optic makers build for the RMR. Pistol makers cut for the RMSc. They are not aiming at the same target.

Why are there footprints no pistol is cut for?

Five of the eleven footprints sit on zero pistols natively. ACRO has 5 optics and no slide milled for it. The Holosun 509T has 8, the Holosun EPS has 9, Docter has 6, and C-More STS has 1. None of them show up as a factory cut anywhere in the data.

They still get used. They reach pistols the long way, through an adapter plate that bolts to the slide and presents the footprint the optic expects. That is how most enclosed-emitter optics, the ACRO and the 509T included, end up on a Glock or a Sig. The slide was never cut for them, so the plate does the translation.

Who actually makes all these optics?

One company, mostly. Holosun makes 57 of the 134 optics in the set. That is 43 percent. The next brand down is Sig Sauer at 9, then Trijicon, Vortex, and Bushnell.

It goes further than the headline. Holosun also makes 26 of the 47 RMR optics, which is more RMR-pattern sights than Trijicon sells, and Trijicon invented the RMR. You can have whatever opinion you want about the brand. The data does not care. Close to half of this entire market is one manufacturer.

The full map

Footprint	Optics	Pistols
RMSc	32	80
Holosun K	8	26
Glock MOS	1	16
Walther PDP 2.0	1	10
RMR	47	7
DPP (DeltaPoint Pro)	16	2
Holosun EPS	9	0
Holosun 509T	8	0
Docter	6	0
ACRO	5	0
C-More STS	1	0

What each footprint actually is

The table tells you what fits what. It does not tell you what these patterns are or why you would choose one, so here is the short version of each cut that matters.

RMSc. A compact pattern from Shield Sights, built for slim and micro-compact slides. It is the standard the carry market settled on, which is why 80 pistols in the set use it and almost none of them are full-size duty guns. If you bought a single-stack or micro nine in the last few years, this is almost certainly your cut.

RMR. Trijicon’s full-size pattern, two screws and two locating posts up front. It came out of the duty and competition world, where slide size is not the limiting factor, and the optic catalog grew up around it. That history is why 47 optics chase a cut only 7 pistols are milled for.

Holosun K. Holosun’s own micro pattern, in the same size class as the RMSc but not interchangeable with it. It rides on 26 pistols, second only to the RMSc, because the K-series optics are cheap and sold everywhere.

DeltaPoint Pro. Leupold’s pattern, wider than most and easy to spot by shape. Sixteen optics use it, but only 2 pistols are cut for it, so on nearly every gun it arrives on a plate.

The enclosed group: ACRO, Holosun 509T, Holosun EPS. These seal the lens and emitter inside a housing instead of leaving the emitter exposed, which makes them the rugged, weather-sealed end of the market. Not one of them is cut into a factory pistol slide anywhere in the data. Every single one reaches a gun through an adapter plate, which is worth knowing before you fall for one.

Docter and C-More STS. Older patterns with a handful of optics each and no modern pistol cut behind them. They turn up on competition builds and older guns, and you can mostly set them aside unless you already own the optic.

Glock MOS and Walther PDP 2.0. These are not optic footprints at all. The Glock MOS slide is machined for a set of adapter plates rather than for any one optic, and the Walther runs its own version of the same idea. Exactly one optic mounts to each directly. Everything else bolts to a plate, and the plate bolts to the slide.

Why the two markets drifted apart

Our read is that timing caused the split. The RMR sold hard to police and military buyers years before red dots went mainstream on carry guns, so by the time optic makers were choosing a pattern to build around, the RMR was already the safe bet, and they copied it. Then the carry market showed up, and the guns driving it were slim. A full-size RMR cut does not fit a micro-compact slide, so pistol makers reached for the smaller RMSc and Holosun K patterns instead. One side of the market had standardized on a duty-era footprint while the other side needed something that fit a pocket gun. The adapter plate exists to bridge that gap, which is why so much of this market runs through one.

How we built this, and how to check it

These counts come straight out of the dataset. Every fit is tied to a source, usually a manufacturer or retailer page that states the compatibility, and a fit with no source does not ship to the site. The footprint assignments are curated and reviewed, and the numbers in this post were recomputed from the live data for this piece rather than carried over from memory or rounded for effect. If a figure here looks wrong to you, the underlying records are public. Open the footprint list or the dataset page and the source behind any fit is a click away. That is the entire point of the project. You should not have to take our word for it.

So where should you start?

Start from the gun, not the optic. Your slide’s cut is the one thing you cannot change after the fact, so it is the constraint that decides everything downstream. Find your pistol, read its footprint, and the optic list collapses from everything on the shelf to the few that will actually bolt on. If your cut is a common one, an RMSc or a Holosun K, you have plenty of room to choose on price and features. If you have your heart set on an enclosed optic like an ACRO, plan on a plate from the start and budget for it. The full numbers, with a source on every fit, live on the dataset page, and you can start from any cut on the footprint list.