This is a EOTech known as the XPS2, model XPS2-300.
The XPS2 is the shortest" smallest and lightest EOTech model holographic weapon sight available without night vision. Its size and weight make it convenient for hunters and law enforcement officers to carry. It is also fast and runs on a single 123 battery. The compact" single-lithium-battery configuration leaves more rail space than ever for rear iron sights or magnifiers.
Features:
Water Resistant
Fits weaver or MIL-STD-1913 rail
XPS2-2 300BLK reticle