Includes special adapter for Beretta 390 magazine cap; adapter also included for most pump and auto magazine caps, Wood screw base for buttstock, Swivel Lock spring-loaded plunger and a knurled, threaded sleeve eliminates accidental opening of the swivel, Does not fit Browning 2000, W-Inchter 1400, Ithaca 37, Savage 30, Sears 21 or Stevens pumps, Closed Link technology creates a permanent ring bond