What red dots fit the SIG Sauer P320-M17 / M18?
Page last updated . Data compiled September 2026 by Andrew Terrebonne.
46 of the 77 optics tracked here mount to this slide, and 10 of those need no adapter plate. This slide uses SIG P320 optic cut (Romeo1Pro pattern).
No plate neededPlate neededDoesn’t fit
Mount systemSIG P320 optic cut (Romeo1Pro pattern)
Optics that fit46 of 77
No plate needed10
Plate to buy36
Plate to slideper plate instructions
Slide tappedM4 × 0.7
New to red dots? What footprint, plate, co-witness and the rest mean
Cheapest ways to mount it
Same slide cutThe SIG Sauer P320 X-Carry, SIG Sauer P320 XCompact, SIG Sauer P320 XFive Legion, SIG Sauer P320 XTen, SIG Sauer P320 AXG Legion / AXG Pro and SIG Sauer P320 Spectre Comp share this slide's optic cut
(SIG P320 optic cut (Romeo1Pro pattern)), so the optics, plates and screws below are the same for
all of them. What differs between the models is under "On this model", where there is anything.
How this slide mounts an opticOptic-ready P320 slides are milled for SIG's own Romeo1Pro pattern, which also takes DeltaPoint Pro-footprint optics: SIG sells its DPP-footprint ROMEO-X PRO for the optic-ready P320. Everything else goes on through a plate, and there are plenty to choose from.
On this modelMost M17/M18 slides carry the Romeo1Pro cut and take the same plates as the X-series. Confirm yours isn't the older Romeo1 pocket or a SIG-LOC slide; all three exist under this name.
Every optic, and how it mounts
Adapter plates for the SIG Sauer P320-M17 / M18
| Plate | Gives you | Source | Price |
|---|---|---|---|
| P320 → RMR / SRO / RCR / Holosun C | Trijicon RMR Trijicon RCR | C&H Precision ↗ | $25–60 |
| P320 → ACRO / Steiner MPS | Aimpoint ACRO | C&H Precision ↗ | $25–60 |
| P320 → Holosun 407K / 507K / Vortex Defender-CCW / Olight Osight S | Holosun K Shield RMSc | C&H Precision ↗ | $25–60 |
| P320 → Holosun EPS / EPS Carry / SCS CarryA separate plate from C&H's 407K / 507K one; M4 plate screws included. | Holosun K | C&H Precision ↗ | $25–60 |
| P320 → Holosun 509T | Holosun 509T | C&H Precision ↗ | $25–60 |
| SIG P320X Optics Ready RMS/SMS Mount (MNT-P320X-SMS/RMS)Shield's own mount for Shield-footprint sights on the P320X optics-ready slide. Shield says a compact sight such as the RMSc leaves a border of the plate showing. Two M4 button-head screws and an Allen key in the box. | Shield RMSc | Shield Sights ↗ | $25–60 |
GuidesSuppressor-height sights: will your irons co-witness? · Installing a red dot: what the makers say
Check a specific pairing
Open the fit checker with this pistol selected, or click any "how it mounts" cell above for that pairing's verdict and build sheet.
Deciding between a few? Compare 3 popular optics on this slide side by side: window, weight, emitter, cost to mount and co-witness.
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