This is the same OEM polymer rear flip sight that is equipped with the KRISS Vector SMG. This sight is extremely low profile, designed to tuck completely out of vision when folded, sitting a mere 14.22mm above the rail surface. The Defiance Rear Sight features two apertures, 1.5mm diameter and 4.5mm diameter, for different lighting and shooting conditions. Additionally, the rear sight folds down completely flat regardless which aperture is in use, in order to be as user friendly as possible. Finally, the large, textured, adjustment knob makes windage changes with gloves simple and easy.NoteLength Folded 2.25"Height Folded .56"Width at Base 1.19"Width at Body 1.19" Large Aperture Diameter .18"Small Aperture Diameter .06"