I have 3 of these, keeping one for my own MP5 build. Has a pressure switch on one side and on/off button on the other side to operate the flashlight option - no strobe? Takes 123 batteries. Much wider, deeper than the stock versions for your larger battery options or for your HPA FCU and batteries. Check out Brain Explorer's YouTube...he had a build to house his batteries for his video stuff? $125 each, shipped thru the app. Last pic shows installation on MP5...