In this guide, we will explain the differences in pistol red dot footprints available on the market.
Often, pistols are advertised as “optics-ready.” However, that doesn’t necessarily mean that a pistol can accept any red dot sight. There are different red dot footprints, and not all red dots will fit on every handgun, despite the advertising.
I am an engineer with over 25 years of experience with handguns and red dot optics. I also carry everyday and shoot handguns in competitions.
I have personally experienced how confusing it can be to interpret the different red dot footprints. Retailers and manufacturers rarely explain the red dot footprint on their handguns in a way that’s easy to understand – if they even mention it at all.
I have created this guide based on my own experiences and research to make it easier for you. Keep reading to learn everything you need to know to figure out if a red dot is compatible with a specific handgun.
Red Dot Footprints – A Simple Guide for Concealed Carry Handguns
Even if you have an “optics ready” concealed carry handgun, it unfortunately doesn’t mean you can just mount whatever red dot sight you want on it. There are different standards of mounting footprints on the market today.
Handguns that are “optics ready” have a series of holes and posts that are machined into the top of the slide. This machined surface on the slide is called a “red dot footprint.” It enables you to attach a red dot accurately and securely to the slide.
When you purchase an optics-ready handgun, most have a cover plate on them so you can use the iron sights if you prefer. If you have not already, be sure to read our iron sights vs red dot guide for the pros and cons of each. Also check out our testing of the best pistol red dot sights and our top picks before you buy.
Before we get into the actual footprints, it is important to understand the sizes.
Red Dot Footprint Size
The size of the slide on your handgun determines the size of the red dot you can mount on it and the footprint.
For concealed carry handguns, there are two basic sizes. They get called many different things, as there isn’t a regulated sizing guideline. For our sake, we will call them full-size and compact. Note that I am talking about the width of the slide and not the overall size of the handgun.
Full-size slides are about 1.0 – 1.1 inches wide. These include handguns like the Glock 19, Walther PDP, and H&K VP9.
Compact slides are about 0.8 – 0.9 inches wide. These include the Sig P365, Springfield Hellcat, and Glock 43.
This is important to remember since it will help you narrow down which red dot sights will work for your handgun. You don’t want to order a full-size red dot for your compact handgun or vice versa.
You can figure out the size of your pistol’s slide by measuring it or looking at the manufacturer’s specifications.
Optics Ready Handgun Adapter Plates
Before getting into the different footprints, it is also important to understand if your optics-ready handgun needs adapter plates or not.
Adapter plates are a second plate that mounts to the pistol slide. The advantage of this is it allows me to mount red dots with different footprints on my handgun.
The disadvantage of adapter plates is they raise the red dot higher on the slide. Sometimes, this results in the current iron sights no longer being useful. On some handguns, the adapter plate replaces the rear sight.
If you are used to using the iron sights, you will have to present the handgun in front of your eye slightly lower with the red dot since it sits up higher on the slide with the adapter plate.
Adapter plates also introduce more screws that can come loose. These should be torqued properly and checked periodically.
Handguns like the Glock 19 MOS and the Walther PDP have adapter plates that can be used for all the common red dot footprints. Some red dots are made to bolt directly to these guns; however, they are not that common yet. Depending on the red dot, these are more desirable than using the adapter plate, in my opinion. C&H Precision has a number of direct mount red dots.
Handguns like my Sig P365 shown below have a common red dot footprint (RMSc and Holosun K footprint in this case) and do not need adapter plates.
If you need an adapter plate for your handgun, C&H Precision has a huge selection and they are easy to find on their website by filtering the list.
Full-Size Red Dot Footprint
I’ve seen larger pistol red dots be called mini reflex sights, which adds to the confusion. Red dots started out being used on rifles and then were reduced in size, hence the term “mini.” All pistol red dots are technically “mini” based on this definition.
In general, these red dots are about 1.25 inches wide and 1.75 inches in length and fit on a full-size handgun slide.
Below are the most common red dot sight footprints you will see for full-size handguns.
Trijicon RMR Footprint
This is the most common footprint today for full-size handguns. Trijicon developed it for their RMR (Ruggedized Miniature Reflex) red dot. It has two screws and two posts to locate the red dot on the slide.
Some popular red dots with the RMR footprint include:
- Trijicon RMR Type 2
- Trijicon SRO
- Holosun 407C
- Holosun 507C
- Holosun 507 Comp
- Viridian RFX35
- Primary Arms Classic Series Mini
- C&H Precision EDC-XL
This footprint was popular in the past but has died out considerably. Most new red dots that are introduced have the RMR footprint instead. Still, some handguns have adapter plates that can be used to mount red dots with this footprint. This footprint has two screws and four posts to locate the red dot on the slide.
Some popular red dots with the Docter/Noblex footprint include:
Leupold Delta Point Pro Footprint
This footprint is not as common as the RMR and is almost exclusively dedicated to the Leupold Delta Point Pro red dot. This footprint has two screws and four posts to locate the red dot. It is very similar to the Shield RMS footprint but has larger posts (4.2mm in diameter vs 3.8mm). This means that a Delta Point Pro sight will fit on a Shield RMS mount; however, the posts will be loose, so it is not recommended.
The Sig Sauer P320 optics-ready handgun has this footprint, so no adapter plates are needed.
Common red dots with the Delta Point Pro footprint are:
Aimpoint ACRO Footprint
Aimpoint created this footprint for their Acro red dot sights. These are larger, fully enclosed red dots that are uncommon for concealed carry. Instead of screws and posts, this footprint mounts to a rail system with a side lug that is tightened down. Note that while similar to Picatinny rail mounting, this footprint is different and will not mount to a Picatinny rail directly.
Also note that many adapters are made for this footprint, so you can adapt an ACRO red dot to virtually any optics-ready handgun.
Common red dots with the Aimpoint ACRO footprint:
Compact Size Red Dot Footprints (Micro)
These red dots are called “micro,” which are smaller than “mini.”
These red dots are about 0.95 inches wide and 1.6 inches in length and fit on compact handgun slides.
Below are the most common red dot sight footprints you will see for compact handguns.
Shield RMS and RMSc Footprint
Shield designed this footprint for their compact red dots that fit on thinner handgun slides like the Sig P365 and Springfield Hellcat. This footprint has 2 screws and 4 posts, similar to the Docter and Delta Point Pro footprints. This is probably one of the more confusing footprints since the two sizes have similar names.
You will often see RMS (or Shield RMS) and RMSc footprints. Basically, the two screws and four sockets are in the same place on both. Just the overall size of the red dot is larger on the RMS. So, an RMSc red dot will fit on both (because it is smaller), but the Shield RMS footprint may be too big for an RMSc slide or adapter plate.
The dimensions of typical red dots with this footprint are:
- Shield RMS – 42mm x 25mm x 23mm
- RMSc – 40mm x 23mm x 22mm
Still confused? I don’t blame you. You’d think they would have made a universal measurement system for red dots, but alas, we’re stuck weeding through confusing measurements.
If you have a Sig P365 or Springfield Hellcat and any variants, they all have a Shield footprint on the slide. So, any red dot that says it is a Shield or RMSc will bolt directly to it.
Some popular red dots with the Shield and RMSc footprint are:
- Sig Sauer Romeo Zero
- Sig Sauer Romeo-X compact
- Viridian RFX 11 and RFX15
- Vortex Defender
- Primary Arms Classic Series Micro
- C&H Precision EDC
Holosun “K” Footprint
Holosun designed this footprint, which is very similar to the Shield and RMSc footprints. Instead of four posts, the two rear posts have been removed, and the two front posts have been shortened in height. This was done to make these red dots waterproof.
This means if you have an optics-ready pistol with a strict Shield RMSc footprint, these red dots will not mount without an adapter or modifications.
Some handguns that have the Shield RMSc footprint that will not work for the Holosun K footprint are:
Some handguns have an optics-ready footprint on them that are Shield RMSc and Holosun K ready. Guns that work with both include:
Some popular red dots with the Holosun K footprint are:
Other Red Dot Footprints
In addition to the more “standard” footprints above, there are some other nuances to understand. Some red dot manufacturers and handgun manufacturers have their own footprints.
Holosun EPS and EPS Carry
This is a new red dot and footprint designed by Holosun. It is very similar to the Holosun K footprint above but has two more posts on the front. This means this red dot will fit on slides with a Holosun K-compatible footprint.
The Holosun EPS is designed for full-size handguns and includes an RMR to K adapter plate. So, if your slide has an RMR footprint on it, you are good to go. If your handguns do not, I would advise against using two adapter plates.
The Holosun EPS Carry is designed for compact handguns and includes an RMSc to K adapter plate. So if you have an RMSc slide, this adapter will allow you to mount this or any K footprint red dot.
Handgun Manufacturer Red Dot Mounting Standards
To make things more confusing, some handgun manufacturers have made their own standards. When you buy an optics-ready handgun, it may have one of the standards we mentioned above, or it could have a proprietary standard. While adapter plates are usually needed, there are some red dots that will mount directly to these standards.
Glock MOS Standard
Glock handguns that are optics-ready have their proprietary MOS (Modular Optics System) mounting footprint. This footprint is unique and has two screws near the center of the red dot. An adapter plate is usually used for this standard to convert it to one of the other common ones.
Holosun and C&H Precision makes a red dot that will mount directly to a Glock MOS slide without an adapter plate.
An important note here. The Glock MOS standard applies to the full-size handguns only (like the Glock 19 MOS.) The compact Glock handguns, the Glock 43x MOS, and the 48 MOS do not have the MOS standard (even though they are called MOS.) They have the RMSc footprint and will not work with Holosun K footprints without modification or an adapter plate.
Walther PDP 2.0 Standard
Similar to the Glock MOS, Walther introduced their own mounting standard in the PDP line of handguns. Adapter plates are typically used to mount a red dot to the slide. Holosun and C&H Precision makes a red dot that will mount directly to the Walther PDP 2.0 without an adapter plate.
Note that PDP handguns that were manufactured earlier had the 1.0 standard, which is different than the 2.0. Removing the cover plate to see which standard you have is easy.
Walther offers one free adapter plate for each PDP that you can get with their optic plate request form. They also have a picture of the difference between the 1.0 and 2.0 standards.
Smith & Wesson M&P 2.0 Standard
Similar to the other manufacturers, Smith & Wesson has their own proprietary standard on their M&P 2.0 optics-ready handguns. Adapter plates are typically used to mount red dots with other footprints. Holosun and C&H Precision makes a dedicated red dot for this standard as well.
Heckler & Koch VP9 Standard
H&K V9 optics-ready pistols have this standard. Just like the others, it is different and proprietary and requires adapter plates to mount most optics. Holosun and C&H Precision makes a model for these similar to the other manufacturers.
CZ Optics Ready Standard
CZ’s P10 and Shadow 2 optics-ready pistols have this standard. Just like the others, it is different and proprietary and requires adapter plates to mount most optics. C&H Precision makes a model for these similar to the other manufacturers.
Learn More about Red Dots
Now that you know the standards and what red dots can fit on your handgun, be sure to read our guide on how to mount a pistol red dot and how to zero a pistol red dot. It is much more than just tightening a few screws and making a few adjustments.
Also, see our guide to the best red dots for concealed carry. If you have not followed our concealed carry guide, be sure to, as it contains information not found anywhere else.
Go To: Concealed Carry Guide