The FAB Defense Polymer Rear Sight can be used as both a primary or back-up sight to your current optic. FAB Defense designed these AR 15 Parts with ergonomic angel-wing-shaped shrouds that help center the image with any front sight so that you can accurately use these in conjunction with a front back-up sight or other optic. With an instant spring-locked mechanism for deployment, the FAB Defense RBS will never slip, break, or deform, offering outstandingly reliable performance in the field. Equip the FAB Defense Rear Back-Up Sight on your weapon today for precise views down range every time. Specifications for FAB Defense Top Mounted Deployable Rear Sight: Manufacturer: FAB Defense Condition: New Sight Position: Rear Gun Model: M16, M4, AR-15 Gun Make: AR Platform Fabric/Material: Polymer Height: 14 mm Length: 52 mm Illumination Type: Non-Illuminated Hand: Ambidextrous FAB Defense Polymer Rear Sight, 1S0-IRN-RPFUS Can be used as primary or back-up sight Ergonomic angel-wing-shaped shroud helps center the image with any front sight, and when used with a matching FAB Defense FBS Front Back-up Sight, it creates a precise optical tunnel that ensures more accurate aiming and faster target acquisition Dual apertures are 3mm for longer eye relief mounting, low light, and faster target acquisition; and 1.5mm for shorter eye relief mounting and greater accuracy; each is instantly selectable to match conditions Low folded profile is smooth and inconspicuous, and will not snag on gear, webbing, or brush Instant spring-locked deployment mechanism will not slip, break or deform No tools needed for easy, rapid windage adjustments, with positive detent locking Made of extremely durable high-grade polymer and metal Package Contents: FAB Defense Rear Polymer Flip-up Rear Sight, 1S0-IRN-RPFUS