Optic footprint mismatches drive more red-dot returns than any other slide question. The cut on your slide and the bolt pattern on your optic have to match — and the terminology is confusing because "RMR cut," "RMSc cut," and "Holosun K" refer to bolt patterns that are not interchangeable. This guide maps each footprint to the Glock platforms 3CR cuts slides for, explains which optic families share each footprint, and gives you a clean lookup so you can match the slide cut to the optic you already own.
The three pistol optic footprints that matter for Glock slides
Most Glock-pattern optics on the market today use one of three bolt patterns. Each pattern has a specific screw spacing, recoil-lug position, and footprint dimension. They are not cross-compatible without an adapter plate, and adapter plates add height that can interfere with iron sight co-witness on smaller slides.
| Footprint | Origin | Slide Width Suited For | Common Optics |
|---|---|---|---|
| RMR (full-size) | Trijicon RMR | Glock 17 / 19 / 23 / 26 / 34 width | Trijicon RMR, Holosun 507C / 407C, Swampfox Liberty, SRO (with caveats) |
| RMSc (sub-compact) | Shield RMSc | Glock 43 / 43X / 48 slim width | Shield RMSc, Holosun 407K / 507K, Swampfox Sentinel, Sig Romeo Zero / Elite |
| Holosun K ("K-pattern") | Holosun 407K / 507K | Same as RMSc — Holosun K uses the RMSc footprint | Holosun 407K, 507K (these are RMSc-pattern optics) |
Important clarification on the third row: "Holosun K" is not a separate footprint from RMSc. The Holosun 407K and 507K were designed to drop onto Shield RMSc-pattern slide cuts, and they share the same bolt spacing. If you see a slide listed as "Holosun K compatible," it is an RMSc-cut slide. The branding gets confusing because Holosun's own optics get name-dropped, but the cut on the slide is the Shield RMSc pattern.
RMR footprint: the full-size standard
The Trijicon RMR set the bolt pattern that the rest of the full-size pistol optic market copied. Two screws on roughly 0.83" centers, with a recoil-lug post forward of the screws. The footprint is large enough that it needs a slide wide enough to support the optic housing without overhang.
RMR-pattern optics fit cleanly on:
- Glock 17 / Glock 22 slide width (full-size)
- Glock 19 / Glock 23 slide width (compact)
- Glock 26 / Glock 27 slide width (subcompact, see caveat below)
- Glock 34 / Glock 35 slide width (long-slide)
The subcompact caveat: the Glock 26 slide is just barely wide enough to take an RMR. Some manufacturers cut the RMR footprint on G26 slides, others use the smaller RMSc footprint to keep the optic from looking visually oversized. Both work mechanically — the question is whether you want the larger optic on a small slide.
For RMR-cut Glock 19 slides, 3CR stocks the Assembled Glock 19 Gen 3 DLC RMR Slide ($195) and the LFA Cerakote Elite RMR Slide for Glock 19 Gen 1-3 ($160). Both ship with a cover plate so you can run the slide without an optic until you have the right one.
Which optics fit an RMR cut? Trijicon RMR is the obvious one. The Holosun 507C and 407C share the footprint. The Swampfox Liberty is RMR-pattern. The Trijicon SRO is technically RMR-pattern but the SRO has a wider window and some shooters report clearance issues with windowed slides — verify on a specific slide before ordering.
RMSc footprint: the slim-slide standard
Shield Sights designed the RMSc footprint specifically for slim subcompact pistols where a full-size RMR overhangs the slide. The bolt pattern is two screws on roughly 0.92" centers — the longer screw spacing means more secure mounting on a narrower slide, with the recoil lug forward of the screws.
The RMSc footprint is the right call for:
- Glock 43 / 43X / 48 slide width (slim single-stack — this is the primary target platform)
- Glock 26 / 27 (sometimes) — when the manufacturer decides to spec a smaller footprint on the subcompact
For RMSc-cut Glock 43/43X slides, 3CR stocks several options. The LFA Cerakote Combat RMSc Slide for Glock 43 ($160) is the stripped option for buyers bringing their own internals. The LFA Elite RMSc Stripped Slide for Glock 43/43X ($130) is the entry-level stripped option. For assembled and shop-tested, the Assembled Glock 43/43X Black RMSc Slide + Nitride Barrel ($199) and the Assembled Glock 43/43X FDE Elite RMSc Slide ($225) ship ready to drop onto your frame.
Which optics fit an RMSc cut? The Shield RMSc is the original. Holosun 407K and 507K are direct drop-ins (this is what "Holosun K compatible" means on a slide listing). Swampfox Sentinel, Sig Romeo Zero, and Romeo Zero Elite all use the RMSc footprint. For the full optic list including weight and price comparisons, see our existing breakdown of what optics fit a Glock 43 RMSc cut slide.
Glock 26 — the subcompact crossover case
The Glock 26 is the one platform where you have to read the slide listing carefully. Some manufacturers cut RMR on G26 slides; others cut RMSc. Both work — the question is which optic you plan to mount.
The practical reality: if you already own an RMR-pattern optic (Trijicon RMR, Holosun 507C), pick an RMR-cut G26 slide. The 3CR Stripped Glock 26 DLC RMR Slide ($169.99) is the current in-stock RMR-pattern option. If you own a smaller K-pattern optic (Holosun 407K, 507K), look for an RMSc-cut G26 slide. RMSc-cut G26 slides are less common — inventory rotates, so check the Glock slides category for current availability.
One more wrinkle on the G26: the slide is short enough that even an RMR-pattern optic sits visually large. Some shooters prefer the RMSc on the G26 purely for visual proportion. Mechanically either footprint works on the slide width.
Will an adapter plate let me mount any optic on any slide?
Adapter plates exist for almost every Glock-pattern slide cut, and they convert one footprint to another. The trade-off is height. Every adapter plate adds approximately 0.10–0.15" of stack height between the slide and the optic. On a full-size slide this is usually fine — the slide is tall enough that the optic still co-witnesses with suppressor-height iron sights.
On a subcompact or slim slide, that added height can put the optic above the iron sight co-witness line. The optic still works, but you lose the ability to use iron sights as a backup through the optic window. For carry builds, matching the slide cut to the optic directly is the cleaner answer.
Optic screw spec — order this with the slide
RMR-pattern optics and RMSc-pattern optics both use 6-32 thread screws, but at different lengths. On a stripped slide:
- RMR optic mount screws: 6-32 × 7/16" (most builds — verify with your specific optic)
- RMSc optic mount screws: 6-32 × 7/16" (Holosun K and Shield RMSc both)
- Cover plate screws: 6-32 × 1/3" (shorter — for running the slide without an optic)
The strongest recommendation: order the screw kit from your optic manufacturer when you order the optic. Holosun, Trijicon, Sig, and Shield all sell torque-matched screw kits that come with the correct length and threadlocker. Generic hardware works in a pinch but optic-manufacturer kits reduce the risk of stripped slide threads.
Footprint-to-slide-to-optic lookup
| You Own This Optic | Cut You Need | 3CR In-Stock Slide Examples |
|---|---|---|
| Trijicon RMR / Holosun 507C / 407C / Swampfox Liberty | RMR cut | Glock 19 Gen 3 DLC RMR (assembled); LFA Elite RMR G19; Glock 26 DLC RMR (stripped) |
| Holosun 407K / 507K / Shield RMSc / Swampfox Sentinel / Sig Romeo Zero | RMSc cut | LFA Combat RMSc G43; LFA Elite RMSc G43/43X; Assembled G43 Elite RMSc (FDE / Black / ODG) |
| Trijicon SRO | RMR cut (verify window clearance) | Same as RMR row — check slide window profile |
| Leupold DeltaPoint Pro | DeltaPoint Pro cut (not RMR or RMSc) | Not currently stocked as a dedicated cut — DPP requires its own pattern or an adapter |
Bottom line
Pick the optic first. Match the slide cut to the optic footprint. RMR for full-size and most compact builds (Glock 17/19/23/34). RMSc for slim builds (Glock 43/43X/48) and for K-pattern Holosun optics on subcompacts. Skip adapter plates on small slides where co-witness matters. Browse the current selection of cut-specific slides in the Glock slides category and confirm the cut on the product page before checkout.
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