Low profile and lightweight design. Can be used as a primary or back-up sight. Manually adjustable, no tools needed. The Mepro FUBS are tritium-enhanced, self-illuminated front and rear back-up sights designed to provide the shooter secondary sights in case the primary optics go down. Mepro FUBS sights are advanced, low-profile, durable, tritium-enhanced auxiliary front and rear back-up sights. The sights quickly fold up or down depending on the shooters needs. Sight pin elevation is easily and quickly adjusted without tools. Mepro FUBS sights are readily mounted on any 1913 Picatinny rail.table.productattributes, .productattributes td { border-bottom: 1px solid #ddd; border-collapse: collapse; padding: 2px; text-align: left; }