Submersible to 33 ft. (10 m) depth 1'' Weaver or MIL-STD-1913 rail 20 daylight settings - 10 additional settings for Gen I through III+ night vision devices One 123 lithium battery 600 continuous hours at nominal setting 12 at room temp The ''E'' is for ''Extreme.'' The EXPS3 offers true 2-eyes-open shooting and a 7 mm raised base that still allows for iron sight access. It features easy-to-adjust side buttons and an adjustable, locking, quick-detach lever for easy attachment and removal.