Rugged aluminum and steel flip-up rear sight regulates properly with A2-height front sights and can be co-witnessed through an optic. Dual apertures are calibrated for close- and mid-range targets, simply aim through both or fold the first one down and use the second aperture. Easily mounts to a Picatinny receiver rail; locknut is retained by a safety wire, so you can't lose it. Non-snagging lever instantly releases the spring-loaded sight into the ready position. #40L Low Profile is calibrated for 250 and 300 meter combat ranges, with windage adjustable in A 3/4 MOA increments per click. NSN #1005-01-575-3508. Mfg: A.R.M.S. SPECS: Apertures - Steel, matte black. Hardware - Stainless steel, matte black. Base - aluminum, hardcoat anodized, matte black. 23/16" (5.6cm) long, 13/8" (3.5cm) wide. #40L - 5/8" (1.6cm) high from flattop (folded), 15/8" (4.1cm) tall (dep