This is a KRISS USA, Inc Sight, model DA-RSBL00.
Kriss USA Low Profile flip up rear sight is the same OEM rear flip up sight that come standard with the Kriss Vector and DKM22 firearm platforms. The sight provides you with an extremely low profile rear sight which will tuck completely out of the way when folded resting at a slim .56" when folded down in the stowed position. This particular rear sight has dual apertures and a wide range of Windage adjustment. The large textured adjustment knob makes windage changes simple and easy especially if you are operating with a gloved hand.
Features:
Low Profile Flip Up Rear Sight
2.25 length folded;1.19 width at base
1.19 width at body;.56 folded height
Same sight that comes with the Vector