FBS is an advanced low-profile durable auxiliary front sight. It can be used with any rear sight but has been designed to provide an extreme optical advantage when paired with the FAB Defense RBS Rear Back-up Sight. Sight pin elevation is easily and quickly adjusted without tools. - FBS is readily mounted on any 1913 Picatinny rail making it ideal for use on M4 / AR-15 / M-16 platforms and on the FAB Defense KPOS. - Advantages: - Can be used as a primary or back-up sight - Ergonomic angel-wing-shaped front shroud helps center the image with any rear sight but when used with a matching FAB Defense RBS Rear Back-up Sight it creates a precise optical tunnel that ensures more accurate aiming and faster target acquisition - 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 elevation adjustments with positive detent locking - Made of extremely durable high-grade polymer and metal - Compatibility: - All 1913 Picatinny rails - The FBS should never be mounted on a railed gas block