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 Military Grade reinforced, super tough polyamide, MADE IN THE USA.BUPSWR Features and Functions:" Low profile snag resistant design" Shroud protects aperture from debris and impact damage" Dual peep, same plane aperture allows for perfect co-witness" Infinite MOA" Unique closure with either aperture deployed" Can fold to the rear, the correct direction if dropped" Sight works in conjunction with all standard height front sights" Manufactured using a specially developed Military Grade reinforced, super tough polyamide" Flip Up" International shipments DO NOT require an export license, this item ships freely.