Lightweight, streamlined backup sights are built on the K.I.S.S. principle to ensure the tactical operator has a reliable, always-deployed sighting option if the main optic fails. One-piece design slides easily on a MIL-STD 1913 rail and clamps securely with a single machine screw. Rounded edges and recessed attachment screws resist snagging on other gear. A1.5 Rear Sight combines the windage adjustment drum of the original USGI A1 rear sight and a flip-up A2 aperture with large .190" peep for close range and .060" peep for long-range targeting. Compact profile doesn't hang over the rear of the receiver to interfere with the shooter's access to the charging handle. Mfg: Daniel Defense SPECS: 6061 T6 aluminum, Type III hardcoat anodized, matte black. A1.5 Rear Sight -13/8" (3.5cm) long, 1A 1/4" (3.2cm) wide, 15/8" (4.1cm) high from top of receiver rail to top of sight housing. 1.7 oz. (49g) weight.