The number-one reason a pistol red dot doesn't fit is a footprint mismatch — the screw-hole and recoil-lug pattern on the bottom of the optic has to match the cut milled into your slide (or the adapter plate it uses). This chart maps the common footprints to the optics we stock and the pistols they're usually found on, so you can order with confidence. New to footprints? Start with our plain-English guide to RMR vs RMSc footprints.
Always confirm your exact model. Optics-ready pistols vary by generation and plate kit — use this as a starting point, then verify against your pistol's plate/manual, or contact us with your exact model and we'll confirm a compatible optic.
Footprint compatibility chart
| Footprint | Optics we stock | Commonly found on | Notes |
| RMR (Trijicon) | Trijicon RMR Type 2, SRO; Holosun 507C / 407C (X2 & X3), 508T, 507COMP | Glock MOS, Walther PDP, Springfield XD-M Elite OSP / Prodigy, S&W M&P CORE, CZ optics-ready — usually via the matching MOS adapter plate | The most widely supported full-size / duty standard. Browse RMR-footprint optics. |
| RMSc / K (Shield RMSc; Holosun calls it the K footprint) | Holosun 507K / 407K (X2), EPS Carry; SIG ROMEO-X Compact | SIG P365 / P365X / XL, Glock 43X / 48 MOS, S&W Shield Plus / CSX, Springfield Hellcat OSP, Ruger Max-9, Taurus GX4 | The micro-compact / carry standard. Browse RMSc-footprint optics. |
| 509T (Holosun) | Holosun HE509T / HS509T (titanium, enclosed) | 509T-cut slides, or any Picatinny rifle via the ADM AD-509T mount | A dedicated enclosed-optic footprint. See the AD-509T QD mount. |
| RCR (Trijicon) | Trijicon RCR (enclosed) | Trijicon RCR-pattern slides / plates | The RCR uses its own dedicated footprint — confirm your slide or plate supports it. |
| RMR HD (Trijicon) | Trijicon RMR HD | RMR-pattern slides (updated) | The RMR HD's footprint is updated and not identical to the classic RMR — check mount / plate compatibility before buying. |
RMR footprint — full-size & duty
Set by the Trijicon RMR, the RMR footprint is the most broadly supported pattern for full-size and duty pistols. On most optics-ready guns (Glock MOS, Walther PDP, Springfield OSP) it's fitted via the included adapter plate that matches the RMR pattern. Optics in our range on this footprint include the Trijicon RMR and SRO and the Holosun 507C, 407C, 508T and 507COMP.
RMSc / K footprint — carry & micro-compact
The RMSc footprint (Holosun's K footprint) is smaller and narrower for slim carry pistols where an RMR cut won't fit. If you carry a SIG P365, Glock 43X/48, S&W Shield Plus, Springfield Hellcat or Ruger Max-9, this is almost certainly your pattern. Our picks here include the Holosun 507K and 407K and the sealed EPS Carry family. Many EPS Carry models even ship with an RMSc-to-K adapter plate for extra slide compatibility.
Enclosed footprints — 509T, RCR & EPS
Sealed (enclosed) optics protect the emitter from lint and rain — ideal for carry and duty. The Holosun 509T and Trijicon RCR each use their own footprint, while the Holosun EPS Carry sits on the RMSc/K pattern. Compare them all in our enclosed red dot sights collection, and read enclosed vs open to decide.
Other footprints you may see
Beyond the patterns above, you'll also encounter the Leupold DeltaPoint Pro (DPP), the Docter/Noblex pattern (Vortex Venom/Viper, Burris FastFire) and the Aimpoint ACRO. These are separate standards — if your slide or plate is cut for one of those, you'll need an optic designed for it.
How to find your footprint
- Check your optics-ready pistol's manual or the markings on its included adapter plates.
- Match the plate to the optic you want — plate kits are footprint-specific.
- When in doubt, measure the slide cut against the maker's footprint diagram, or just ask us.
Ready to choose?
Shop by footprint to guarantee a fit: RMR Footprint for full-size pistols or RMSc Footprint for carry guns. Browse the full pistol dot sights range, or read our best pistol red dot sights and best optics for concealed carry guides.
Frequently asked questions
Which red dot fits a SIG P365 / Glock 43X / Hellcat?
All three use the RMSc (Holosun K) footprint — optics like the Holosun 507K, 407K and EPS Carry fit, often directly or via the included K-adapter plate.
Which red dot fits a Glock MOS / Walther PDP / Springfield Prodigy?
These full-size optics-ready pistols typically take an RMR-footprint optic (Trijicon RMR/SRO, Holosun 507C) using the matching MOS adapter plate from the pistol's plate kit.
Is the RMR HD the same footprint as the classic RMR?
No — the RMR HD uses an updated footprint that isn't identical to the original RMR. Confirm mount/plate compatibility before buying.
Can I adapt one footprint to another?
Sometimes, via an adapter plate — but always confirm the specific plate supports both your optic and your slide before ordering.
UK Delivery & Support
Every optic on this chart is UK-stocked and dispatched tracked from our UK warehouse — no import duties or customs delays — with UK-based support if you need help confirming a fit.