Glock MOS Optic Plate Compatibility Chart for RMR and K Footprints

Choosing the correct Glock MOS optic plate requires checking two separate mounting interfaces: the optic-ready cut on the pistol and the footprint of the red dot sight. Both must match before an optic can be mounted correctly.

For standard Glock MOS pistols, StoneIron Defense offers two optic plates for different footprint standards. The SID-2258 supports the listed RMR-pattern optics, including the Trijicon RMR, Trijicon SRO, Holosun 407C, 507C, and 508T. The SID-2259 supports the listed K-footprint optics, including the Holosun 407K, 507K, EPS, and EPS Carry.

These plates serve different purposes and are not interchangeable at the optic mounting interface. A Holosun 507C, for example, uses a different footprint from a Holosun 507K, despite the similar model names.

This guide explains which Glock models StoneIron Defense lists as compatible with each plate, how RMR and K footprints differ, and what to verify before choosing an adapter.

Which Glock MOS Optic Plate Do You Need?

The correct plate depends on your Glock's mounting system and your optic's footprint.

This comparison applies to the standard Glock MOS models supported by the respective StoneIron Defense product listings. It does not establish compatibility with Slimline MOS, MOS-K, Gen 6 ORS, or aftermarket slide cuts.

How Does Glock MOS Optic Plate Compatibility Work?

Glock's Modular Optic System (MOS) provides an optic-ready slide with a recessed mounting area designed to accept an adapter plate. The plate creates the mounting interface required for a particular optic footprint.

There are two separate compatibility considerations:

• 1. Pistol-to-plate compatibility: The adapter plate must match the factory mounting system and the specific Glock model. Standard MOS, Slimline MOS, Slimline MOS-K, and Gen 6 ORS are not interchangeable mounting platforms.
• 2. Plate-to-optic compatibility: The upper mounting surface of the adapter plate must match the optic's footprint, including its mounting holes and locating features.

An RMR-pattern plate will not automatically accept a K-footprint optic. The optic's model number alone is not sufficient to establish compatibility.

Glock's official optic mounting documentation provides additional information about its different mounting systems.

Which Glock Models Are Compatible With SID-2258 and SID-2259?

StoneIron Defense lists the following standard Glock MOS models for its two plates.

Important: The Glock 40 MOS appears on the SID-2258 compatibility list but is absent from the SID-2259 list. Do not assume that compatibility with one plate establishes compatibility with the other. Contact StoneIron Defense to confirm SID-2259 compatibility before ordering for a G40 MOS.

Always check the exact product listing for the latest supported model information.

What About Glock 43X MOS and Glock 48 MOS?

The Glock 43X MOS and Glock 48 MOS use Slimline optic mounting cuts rather than the standard full-size MOS adapter-plate interface.

Glock identifies two Slimline configurations:

• Standard Slimline MOS: Designed around the Shield RMSc footprint.
• Slimline MOS-K: Designed to accept Holosun K or RMSc footprints without a separate adapter plate.

These configurations should not be treated as interchangeable. Check the pistol's exact slide configuration and Glock item number before selecting an optic.

Neither SID-2258 nor SID-2259 is listed for these Slimline models.

Does Glock Gen 6 Use Standard MOS Plates?

Do not assume compatibility between standard MOS plates and Gen 6 ORS plates.

Glock's Gen 6 Optic Ready System uses a separate factory mounting architecture. Standard-frame Gen 6 pistols come with three optic plates for supported optics, but this system is distinct from the earlier standard MOS platform.

Consequently, the SID-2258 and SID-2259 compatibility information in this guide applies to the standard MOS models listed by StoneIron Defense, not Gen 6 ORS pistols.

For additional details, consult Glock's official Gen 6 Optic Ready System documentation.

Do Holosun 407K and 507K Use the Same Footprint as 407C and 507C?

No. The C and K versions use different mounting patterns.

The Holosun 407C and 507C use the RMR footprint, while the 407K and 507K use Holosun's smaller K footprint.

This distinction matters when selecting an adapter plate. Two optics from the same product family can have different mounting dimensions and locating features.

For standard Glock MOS pistols, StoneIron Defense lists the SID-2259 for the Holosun 407K and 507K.

What About Holosun EPS and EPS Carry?

The Holosun EPS family requires additional attention when checking mounting compatibility.

Holosun identifies the EPS Carry as using its K footprint and includes an RMSc-to-K adapter plate with the optic. StoneIron Defense lists both the EPS and EPS Carry as compatible with SID-2259.

However, an optic's included adapter does not automatically establish compatibility with every pistol mounting system. Check the complete mounting combination against the optic and plate manufacturers' specifications.

For standard Glock MOS applications, refer to the SID-2259 Glock MOS K-Footprint Optic Plate.

SID-2258 vs. SID-2259: What Is the Difference?

StoneIron Defense manufactures both plates for standard Glock MOS pistols. Their main distinction is the optic footprint they are designed to support.

Both plates are manufactured from stress-relieved, crack-inspected 4140 billet steel. Their construction specifications include CNC machining, heat treatment, and a black nitride finish.

The product listings also specify the following included hardware:

• Precision-fit plate mounting screws
• Model-specific optic mounting screws
• T10 Torx installation tool
• M3 Allen key

The SID-2258 product listing specifies a limited lifetime warranty. Check the individual product listing for current warranty terms and exclusions.

The decision between these two plates should be based on the optic's mounting footprint, not on the pistol model alone.

What Should You Check Before Buying a Glock MOS Adapter Plate?

Before purchasing an aftermarket adapter plate, verify the following details:

1. Exact Glock model: Confirm the complete model designation and MOS configuration.
2. Generation: Identify whether the pistol uses standard MOS, Slimline MOS, MOS-K or Gen 6 ORS.
3. Factory slide interface: Do not assume that all optic-ready Glock slides share the same mounting dimensions.
4. Exact optic model: Distinguish between models such as the Holosun 507C and 507K.
5. Optic footprint: Confirm whether the optic uses RMR, K, RMSc or another mounting standard.
6. Plate SKU: Match the footprint to the appropriate product listing.
7. Supported firearm models: Confirm that your exact Glock model appears on the plate manufacturer's compatibility list.
8. Included hardware: Check that the required mounting screws and other listed components are supplied.
9. Installation requirements: Follow the firearm and optic manufacturers' documentation and StoneIron Defense's recommendation to have installation performed by a qualified gunsmith.

These checks help prevent ordering a plate that matches the optic but not the pistol, or vice versa.

Frequently Asked Questions

Are Glock 17 MOS and Glock 19 MOS optic plates interchangeable?

StoneIron Defense lists both the Glock 17 MOS and Glock 19 MOS as compatible with SID-2258 and SID-2259. The correct plate still depends on the optic footprint. Always verify the exact product listing before ordering.

Does a Glock MOS plate support the Trijicon RMR?

Yes, when the plate is designed for the RMR footprint and supports the specific Glock model. StoneIron Defense lists its SID-2258 plate for the Trijicon RMR on supported standard Glock MOS pistols.

Can the Trijicon SRO use an RMR-pattern Glock MOS plate?

The Trijicon SRO shares the RMR mounting pattern. StoneIron Defense explicitly lists the SRO as compatible with SID-2258.

Are Holosun 407C and 507C compatible with RMR-pattern plates?

Yes. Both optics use the RMR mounting pattern and are listed as compatible with the SID-2258.

Do Holosun 407K and 507K fit the same plates as 407C and 507C?

No. The 407K and 507K use the Holosun K footprint, which differs from the RMR pattern used by the 407C and 507C. For supported standard Glock MOS pistols, StoneIron Defense lists SID-2259 for the K models.

Can a Glock 43X MOS use SID-2258 or SID-2259?

Neither product is listed for the Glock 43X MOS. The pistol uses a Slimline mounting configuration rather than the standard MOS adapter-plate interface.

Are Glock Gen 6 ORS and standard MOS plates interchangeable?

They are separate mounting systems. Glock Gen 6 ORS uses its own factory optic plate architecture. Do not assume an aftermarket standard MOS plate fits a Gen 6 pistol.

Which StoneIron Defense plate supports the Glock 19 MOS?

Both SID-2258 and SID-2259 list the Glock 19 MOS as compatible. Choose SID-2258 for the supported RMR-pattern optics and SID-2259 for the supported K-footprint optics.

Is the Glock 40 MOS compatible with SID-2259?

The current SID-2259 product listing does not include the Glock 40 MOS. StoneIron Defense lists the G40 MOS for SID-2258, but that does not establish compatibility with SID-2259. Confirm with the manufacturer before purchasing.

Conclusion

Selecting the correct Glock MOS optic plate comes down to matching the pistol's factory mounting system with the optic's footprint.

StoneIron Defense offers two plates for the standard Glock MOS platform:

• SID-2258: Designed for listed RMR-pattern optics, including the Trijicon RMR, SRO and Holosun 407C, 507C and 508T.
• SID-2259: Designed for listed K-footprint optics, including the Holosun 407K, 507K, EPS and EPS Carry.

Both plates use CNC-machined 4140 billet steel and are designed for different optic mounting interfaces.

Before ordering, verify your exact Glock model, mounting configuration and optic model against the relevant manufacturer's documentation. If a combination is not explicitly listed, seek confirmation rather than relying on assumed compatibility.