The Shield Sights Low Pro Slide Mount for Glock 21 lets you mount a red dot to your Glock 21 slide without any milling or gunsmithing. Instead of cutting into your slide, this low-profile mount replaces your factory rear iron sights, giving you a clean, integrated platform for modern optics. It's the straightforward way to add a red dot to one of the most popular defensive and hunting handguns out there—no trips to a gunsmith, no permanent modifications to your gun.

The mount sits flush with Shield Sights' compact optics, particularly the RMSc and SMSc, creating a slim profile that doesn't add bulk to your carry or duty gun. If you're running a standard RMS, SMS, or SMS2 sight, the mount will work but you'll see slight width overhang. The RMSw is compatible, though it may not seal completely since the plate is narrower than the RMSw's gasket.

Built for shooters who want the speed and reliability of a quality optic without the expense or downtime of a slide cut, this mount is a practical choice for anyone running a Glock 21 and ready to upgrade their aiming system.

Key Features

• Replaces rear iron sights—no slide milling required
• Low-profile design sits flush with RMSc and SMSc optics
• Compatible with standard RMS, SMS, and SMS2 sights (with minor overhang)
• RMSw compatible (seal fit may vary)
• Purpose-built for Glock 21 slide dimensions

Specifications

Frequently Asked Questions

Will this mount fit my Glock 21 without gunsmithing?

Yes. The Shield Sights Low Pro Slide Mount replaces your rear iron sights and requires no milling or cutting of the slide.

What red dot sights work with this mount?

The RMSc and SMSc mount flush and are fully compatible. The standard RMS, SMS, and SMS2 will also work but with slight width overhang. The RMSw is compatible, though the seal may not be complete because the plate is narrower than the RMSw's gasket.

Does this mount replace my iron sights?

Yes. The mount includes a slide-in rear sight and mounting plate, replacing your factory rear iron sight.