The FAB Defense FRBS Rifle Sights Kit (brand part no. fx-frbskitt) is a low-profile front and rear back-up sight set designed to mount on any 1913 Picatinny rail, making it a natural fit for M4, AR-15, M16, and FAB Defense KPOS platforms. Built from fiberglass-reinforced polymer and metal, the kit lets shooters adjust elevation and windage without tools, and it works equally well as a primary sighting solution or a compact back-up. The finish is tan, and the FBS half should never be mounted to a railed gas block. It’s a durable, no-fuss upgrade from FAB Defense.

Key Specifications

• Includes both a front (FBS) and rear (RBS) back-up sight for a complete sighting solution.
• Adjusts elevation and windage without tools, using a spring-based locking mechanism.
• Mounts to any 1913 Picatinny rail, fitting M4, AR-15, M16, and KPOS platforms.
• Built from fiberglass-reinforced polymer and metal for durability without excess weight.
• Finished in tan to match desert and coyote-toned builds.
• Folds to a low, sleek profile that resists snagging on gear or webbing when not deployed.

Frequently Asked Questions

What rail does this sight kit mount to? Any standard 1913 Picatinny rail, including M4/AR-15/M16 platforms and the FAB Defense KPOS.

Can I adjust these sights without tools? Yes, both the front and rear sights use a spring-based mechanism that adjusts for elevation and windage without tools.

Can the front sight be mounted on a railed gas block? No, FAB Defense specifies the FBS should never be mounted on a railed gas block.

Buy the FAB Defense FRBS Rifle Sights Kit, Tan

Order the FAB Defense FRBS Sight Kit from our Lubbock, Texas gun shop for fast, insured shipping to your FFL. It’s a rugged, tool-free back-up sight set that’s ready to mount straight out of the box. Browse more of our gun sights selection while you shop.