The FAB Defense Front/Rear Folding Back-Up Sight set (brand part number FXFRBS) pairs a low-profile FBS front sight with a dual-aperture RBS rear sight, both durable enough to run as a primary sighting system or a folding backup. Each sight mounts on any 1913 Picatinny rail, making the set ideal for M4, AR-15, and M16 platforms. The rear sight’s dual apertures give a shooter two aiming options: a 3mm aperture for longer eye relief, low light, and faster target acquisition, and a 1.5mm aperture for shorter eye relief and greater precision, instantly selectable to match conditions. An ergonomic, angel-wing-shaped shroud on both the front and rear sight helps center the sight picture regardless of which sight it’s paired with.

Key Specifications

• Front sight (FBS) functions as a low-profile, durable auxiliary front sight.
• Rear sight (RBS) functions as a low-profile, durable auxiliary rear sight.
• Rear sight offers a 3mm aperture for longer eye relief and faster acquisition.
• Rear sight offers a 1.5mm aperture for shorter eye relief and greater accuracy.
• Apertures are instantly selectable to match conditions.
• Mounts on any 1913 Picatinny rail.
• Ideal for M4, AR-15, and M16 platforms.
• Usable as a primary or backup sighting system.
• Features an ergonomic angel-wing-shaped shroud on both sights.

Frequently Asked Questions

Can these sights be used as primary sights? Yes, both the front and rear sight are durable enough to run as a primary system or as a folding backup.

What do the two rear apertures do? A 3mm aperture gives faster target acquisition and low-light performance; a 1.5mm aperture gives greater precision at longer eye relief.

What rail does this fit? Any standard 1913 Picatinny rail.

Buy the FAB Defense Front/Rear Folding Back-Up Sights, AR-15/M16/M4, Black

Add a durable primary or backup sight set to any Picatinny rail. Order the FAB Defense sight set from our gun sights selection at our Lubbock, Texas gun shop for fast, direct shipping.