Low profile and lightweight design. Can be used as a primary or back-up sight. Manually adjustable, no tools needed. The FRBS 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.table.productattributes, .productattributes td { border-bottom: 1px solid #ddd; border-collapse: collapse; padding: 2px; text-align: left; }