The Back Up Polymer Flip Up Rear Sight with Windage Adjustment (BUPSWR) mounts onto a 1913 Picatinny rail. A flat head screw driver is required to adjust an Infinite MOA. Unlike other backup sights MFT has developed a shroud that shelters the aperture from debris and impact damage when not deployed. A slim profile allows the sight to sit under all current magnifiers and optics. Manufactured using a specially developed reinforced super tough polyamide from DuPont