The new Magpul MBUS (Magpul Back-Up Sight) is a low-cost, injection molded, folding back-up sight. Specifically tailored to theAR15/M16/M4 platform, it conveniently folds down and locks into place but flips up with just a press of the button. Elevation adjustable, this polymer sight deploys instantly at the touch of a finger to provide backup sighting if a primary optic fails. The smooth design reduces snagging on brush or other gear when folded. It quickly mounts to any mil-spec 1913 Picatinny rail – must be mounted on a rail that is on the same plane as the upper receiver rail to witness correctly with rear sight. 1.5” long deployed, 2.5” long folded, 1.2” wide, .5” high folded, 1.5” high extended. Sight post .070″ wide.