The SLR MWS B15 Ver. 2 receiver set is CNC machined out of 6061 aluminum. Individual serial number is engraved on each receiver and the original MWS charging handle, selector and magazine release could be install back on this receiver set. A very nice and neat feature has been added on this Ver. 2 Receiver, which is the ambidextrous bolt release function (all related hardware will be included).