A red dot footprint is the pattern of mounting holes and the body shape on the bottom of the optic. It decides which slide cut or adapter plate the optic can bolt to. Two red dots can look alike and still have different footprints, so match the footprint to your pistol before you pick an optic.
The five you will see most are the RMR, the RMSc, the Holosun K, the DeltaPoint Pro and the ACRO. This post explains each one, which optics share it, and the traps that cost people money. If you want the full picture of how a red dot gets onto a slide, read our post on mounting a red dot on a pistol first.
What Are the Most Common Red Dot Footprints?
Shooting Illustrated rounds up the main ones. Here they are side by side.
| Footprint | Optics on it | Notes |
|---|---|---|
| Trijicon RMR | Trijicon RMR, SRO and RCR | Aftermarket slide makers often default to this pattern |
| Shield RMSc | Shield Sights RMSc | Suited to slimmer pistols |
| Holosun K | Holosun 407K, 507K, EPS and EPS Carry | Nearly identical to the RMSc, without the two rear posts |
| Leupold DeltaPoint Pro | The DeltaPoint Pro | Base for Vortex Defender series footprints |
| Aimpoint ACRO | All ACRO generations and the Steiner MPS | Its own pattern |
The sizes differ too. GunTalk gives the RMR about 18.8 mm between screws and a body about 44 mm long. It puts the RMSc body at about 40 mm, and the DeltaPoint Pro at about 31 mm wide and 46 mm long. Check these against the maker’s drawing before you cut or buy anything.
Which Optics Share a Footprint?
Sharing is where the savings are, and where the mistakes are. EGW, a maker of pistol optic mounts, lists compatible optics for each pattern. Examples from its page:
- RMR pattern: Holosun 407C, 507C and 508T, among others.
- DeltaPoint Pro pattern: Also fits the Shield, Optima and JPoint, and the Holosun 407K and 507K, but only if the rear pins are removed from the base.
- Docter pattern: The Docter, Burris Fastfire 2, 3 and 4, and the Noblex Sight II Plus, among others.
Some slides take certain footprints with no plate at all. Shooting Illustrated says the DeltaPoint Pro pattern fits Staccato 2011 pistols and many SIG Sauer P320 variants, which can accept it directly on their slides.
Notice the DeltaPoint Pro line in the list above. The Holosun K and the DeltaPoint Pro are close, but “close” needs a small change to the mount. That is the kind of detail that decides whether an optic bolts on or sits crooked.
The smaller patterns matter on narrow guns. Shooting Illustrated says the RMSc pattern suits slimmer pistols, including single-stack and double-stack 1911s. A larger footprint can be a poor fit on a slim slide, which is one more reason to check the pattern against your slide and not only against the optic.
Newer plate systems add a wrinkle. Glock says its Gen6 standard-frame pistols come optic-ready with three plates, numbered 02, 03 and 04, for different optics, and that a standard Gen4 or Gen5 MOS pistol comes with one plate that fits Trijicon, Ameriglo and Holosun optics except the 509. Same maker, different systems. Always check the generation.
What About the ACRO and the Holosun 509T?
Both are their own thing. EGW lists the Aimpoint ACRO P-1 and P-2 and the Holosun 509T each as a “unique” footprint, which means they do not use one of the four standard mounts. They need their own mounting solution.
GunTalk describes the ACRO as a clamp-style dovetail mount, with no flat-plate screw pattern. It also says the Holosun 509T usually goes on with an adapter plate, and advises against stacking two plates. If a pistol is not cut for either, plan on a plate that is made for that exact pistol and optic.
How Do You Match a Footprint to Your Pistol?
Work backward from the pistol.
- Find out if the slide has a cut. If it does, find out which footprint. If it has no cut, see our post on mounting a red dot on a pistol for the three options.
- Check “optics ready” carefully. GunTalk says the term does not mean the slide accepts every optic. The footprint still has to match.
- Check the plate list for your model. Glock, for example, says a standard MOS pistol comes with one plate that fits Trijicon, Ameriglo and Holosun optics except the 509. Other optics need other plates. Glock’s page also says its slimline MOS cut matches the Shield RMSc footprint and uses M4 screws, and its MOS-K cut accepts either the Holosun K or the RMSc footprint, using the M3 screws from the optic maker.
- Look up the optic’s manual for screws. Trijicon packs two sets of #6-32 screws with the RMR, and says to torque them to 15 inch-pounds. Other makers differ. Never assume screws from one optic fit another.
Four mistakes come up again and again:
- Buying the optic first. Find the footprint first, then pick the optic.
- Trusting “optics ready” as a promise. GunTalk says the slide still has to match the specific footprint.
- Treating close footprints as the same. The Holosun K and the DeltaPoint Pro need the rear pins removed on the mount, per EGW.
- Stacking plates. GunTalk advises against putting two adapter plates on, as with the Holosun 509T.
Why Does the Footprint Limit What You Can Buy Later?
EGW says the footprint you choose can limit your future optic options. If your slide is cut for one pattern, only optics with that pattern, or a plate for it, will fit. A plate can bridge the gap, and a direct cut skips the plate but is cut for one footprint.
So before you pick a red dot because of the price, ask what footprint it uses, and whether you would want to change optics down the road.
What Can Lakeside Do About Footprints?
We cannot pick the footprint for you, but we can tell you the posted price for the install once you know what you have. Our optic mount is $45, red dot or magnified, on the gunsmithing price list. If you buy the optic from us, we install it for free. Posted prices are for a firearm in factory condition. If other changes have been made, we look at the job first.
Our gunsmithing is light work and does not include complex machining, so we do not post a price for cutting a slide. For a pistol that already has the right cut or plate, that is the simple case. Call or contact us with your pistol model and the optic you are thinking about, and we will tell you what the job looks like before you drive over.
