Buying Guide
Pistol Red Dot Footprints: A Compatibility Guide
Buying a pistol red dot is two decisions, and only one is about the sight. The first is optical — dot size, window, colour, emitter. The second is mechanical: will this optic bolt onto the cut in that slide, or not? A slide sold as “optics ready” is only ready for the one screw pattern it was machined for. This guide sets out the patterns in our pistol optic range, which sights use each, and where an adapter plate bridges the gap.
Why footprints exist, and why “optics ready” means nothing on its own
A footprint is the pattern of mounting screws and locating features under a red dot, mirrored by the milled recess in the slide. It is a mechanical interface, not a brand. No standards body ever set one, so the patterns that stuck came with popular sights — the Trijicon RMR, the Shield RMSc, the Leupold DeltaPoint Pro — and other makers copied one, or invented their own.
So “optics ready” tells you a recess has been machined, and nothing else. Two sights of similar size can be mechanically incompatible; two that look nothing alike can share a pattern. Find the cut your slide was machined for, then match it to the footprint the optic’s maker states. We can verify optics and plates against their manufacturers; we cannot tell you which cut is in your pistol. That belongs to the pistol maker — read their own specification before ordering.
RMSc — the slim pattern for narrow slides
RMSc is the compact pattern originating with the Shield RMSc, used by most slim optics. In our range it is the stated native footprint of the Holosun EPS Core, which mounts direct with no adapter plate required, and of the SIG Sauer ROMEO-X Compact and Compact Rose, both listed by SIG as RMSc (Shield). The Holosun AEMS Micro is also RMSc, supplied with an RMSc-to-AEMS-Micro adapter plate.
What distinguishes it physically is scale. The EPS Core, a direct-RMSc sight, carries a 0.90 × 0.63 in (22.9 × 16.0 mm) window at 1.4 oz (40 g) — compact beside the RMR-pattern sights further down. Browse the pattern at RMSc footprint red dot sights.
Holosun K — adjacent to RMSc, and not a synonym for it
This is the pattern most often got wrong, our own older listings included. Holosun describes the 407K and 507K sights — the HS507K X2, HE507K X2 and HS407K X2 — as “Holosun K footprint (RMSc pattern)”. On the EPS family, though, Holosun is explicit that K is the native footprint and RMSc the adapted one.
- The EPS Carry and RONIN EPS Carry are K footprint native, with an RMSc-to-K adapter plate included — not RMSc-footprint sights, whatever a listing that reverses the two may say.
- The SCS Carry is likewise Holosun K, direct mount, with an RMSc-to-K adapter plate included.
- The full-size EPS is Holosun K with an RMR-to-K adapter plate included — a different plate, for a different cut.
- The EPS Core is the odd one out: direct RMSc footprint, no adapter plate required.
K spans two body sizes: the EPS Carry runs a 0.77 × 0.58 in (19.6 × 14.7 mm) window at 1.23 oz (35 g), the full-size EPS a 0.90 × 0.63 in (22.9 × 16.0 mm) window at 1.4 oz (40 g). So the rule is to read the footprint stated for the exact model, not the family.
507C and RMR — the wide pattern
The Trijicon RMR pattern, which Holosun also labels 507C, is the broad footprint under most full-size pistol optics here. Holosun states it for the HS507C X2 and HS507C X3, the 407C X2 and X3, the HE508T X2, the 407COMP and 507COMP models including the RONIN versions, and the HS507 ProMax. It is the wide-bodied group: the ProMax window is 1.18 × 0.98 in (30.0 × 24.9 mm) at 1.7 oz (48 g). See the pattern at RMR footprint red dot sights.
509T — a footprint that comes with its own plate system
509T is a separate pattern again, sold as a system rather than a single fit. The HE509T X2 in red, green and gold is 509T footprint with an RMR-to-509T adapter plate in the box, so an RMR cut is covered without buying anything extra. The AEMS Macro shares the 509T footprint and also ships with an RMR-to-509T plate.
Holosun also makes 509 plates for named slides: 507C/RMR cuts, CZ P-10, FN 509 Tactical, FNX-45 Tactical and Glock MOS 9mm. Holosun states that the CZ P-10, FN 509 Tactical and Glock MOS 9mm plates take AEMS Macro optics as well as the 509 series.
DeltaPoint Pro — the other wide pattern here
The Leupold DeltaPoint Pro pattern is the stated footprint of every EOTech EFLX in the range, in 3 MOA and 6 MOA, black and tan, and of the whole SIG Sauer ROMEO-X Pro family. The EOTech EFLX CE is dual-pattern: EOTech states Leupold DeltaPoint Pro and Shield RMSc, making it unusually flexible across slide cuts. We do not stock a DeltaPoint Pro adapter plate — the plates here are Holosun K and 509 only — so if your slide is cut otherwise, that plate must be sourced elsewhere.
Direct-mount optics: no footprint to match at all
Holosun’s SCS series sidesteps the problem by machining the optic body to one slide. The specifications state direct mounting to Glock MOS slides for the SCS MOS, SIG Sauer P320 slides for the SCS 320, and equivalents for the S&W M&P 2.0, CZ P-10, H&K VP9 and Walther PDP, the last specified for PDP 2.0 slides with no adapter plates required. Buy the version named for your slide and there is nothing to match; buy the wrong one and no plate will rescue it.
Mounting plates: what the plate route buys, and what it costs
A plate is a machined adapter between slide and optic, presenting one footprint upwards and another downwards. Two families are stocked here. The K plates put K-footprint optics onto 507C/RMR cut slides, CZ P-10 C, FN 509 MRD and Glock MOS 9mm slides; the 509 plates do the same for 509T-footprint optics. Both are aluminium, hard anodised. Three caveats, all from the manufacturers’ own pages:
- Included hardware is not always stated. Holosun confirms mounting hardware with the K plate for 507C/RMR cuts and with the 509 plate for the FNX-45 Tactical. For several others — the K plate for Glock MOS 9mm, the 509 plates for CZ P-10 and FN 509 Tactical among them — it states nothing about screws at all. Not contradicted, simply absent — check the box before assuming you have the fasteners.
- Stated compatibility can be narrower than you expect. Holosun names only the 407K and 507K for the K plate for Glock MOS 9mm; EPS and EPS Carry are not stated there, even though they share the K pattern.
- A plate raises the optic. It is an extra layer between slide and sight, so the dot sits higher than a direct mount would put it. None of the makers publish a thickness figure for the plates we verified, so we cannot tell you how much height in millimetres — expect it to change how the dot sits against any backup iron sights, and check that on the bench.
Where a direct-fit optic exists for your slide, it is the cleaner answer.
Compatibility table
| Optic | Native footprint (as stated by the maker) | Plate |
|---|---|---|
| Holosun EPS Core | RMSc, direct | None required |
| Holosun 407K X2 / 507K X2 | Holosun K (RMSc pattern) | K plates for other cuts |
| Holosun EPS Carry / RONIN EPS Carry | Holosun K | RMSc-to-K plate included |
| Holosun EPS (full size) | Holosun K | RMR-to-K plate included |
| Holosun SCS Carry | Holosun K, direct mount | RMSc-to-K plate included |
| Holosun 407C / 507C X2 and X3, 407COMP / 507COMP, RONIN COMP, 507 ProMax, HE508T X2 | Trijicon RMR / 507C | None on an RMR cut |
| Holosun HE509T X2 | 509T | RMR-to-509T plate included; 509 plates for other cuts |
| Holosun AEMS Micro | RMSc | RMSc-to-AEMS-Micro plate included |
| Holosun AEMS Macro | 509T | RMR-to-509T plate included |
| Holosun SCS 320 / MOS / MP2 / P10 / PDP / VP9 | Model-specific direct mount | None required |
| EOTech EFLX 3 MOA / 6 MOA | Leupold DeltaPoint Pro | None stocked |
| EOTech EFLX CE | Leupold DeltaPoint Pro and Shield RMSc | None stocked |
| SIG Sauer ROMEO-X Compact / Compact Rose | RMSc (Shield) | None stocked |
| SIG Sauer ROMEO-X Pro | DeltaPoint Pro | None stocked |
Enclosed or open emitter — a separate question entirely
Emitter type has nothing to do with footprint and is worth deciding separately. An open-emitter sight bounces its LED off the lens across an open channel; an enclosed sight seals the emitter behind glass, so rain, lint and carbon cannot reach it. Both appear on every pattern here: the RMR-footprint HE508T X2 is open, while the K-footprint EPS and EPS Carry, the RMSc-footprint EPS Core, the 509T-footprint HE509T X2, the AEMS Micro and Macro, the SCS series and the EOTech EFLX CE are enclosed — and the EFLX is an open emitter sight on the same DeltaPoint Pro pattern as the enclosed CE. Pick the footprint your slide demands, then choose the emitter on its merits: see enclosed red dot sights.
Related reading
For the two patterns behind most of the confusion, our RMR vs RMSc footprints guide compares them side by side. If you are still choosing the sight rather than the fit, green vs red dot sights covers reticle colour, and red dot sights holds the full range. Confirm the cut with your pistol’s manufacturer, match it to the footprint stated on the optic, and the rest is straightforward. £5 tracked UK delivery in 7–10 business days.
