The Tippmann Rear Bolt Plug. Fits most Tippmann markers. Spare parts are always a good idea.
This product is used in the following guns: 98 Custom Non-ACT, 98 Custom Pro Response ACT, Alpha Black Basic, Alpha Black Tactical, Alpha Black E-Grip Electronic, Alpha Black Tactical E-Grip Electronic, Bravo One Basic, Model 98, Triumph eXT, Triumph XT, Triumph XL, Gryphon, Carver One, Project Salvo.
The Tippmann Part Number for this product is TA05005.