Plum Crazy AR-15 Improved Gen II Complete Lower Receiver with Patented 6 Position and Aluminum Buffer Tube- Black This version of the E3 Arms complete lower receiver features an Aluminum buffer tube upgrade and also has a Plum Crazy Patented 6 Position Stock. The E3 polymer lower still has all the features that have made this lower famous including reinforced areas where it matters most. ( Sling Swivel Not Included ) Please note that you must be AT LEAST 21 to receive the transfer of this firearm.