The advanced version v2.0 hopup nub for the Tippmann Carbine M4, optimized to work with the adjustment piece and the knurled screw (both available in my shop). All you need now are punch pliers with a 5mm diameter, a rubber eraser and a rail clip. The punched rubber part gets in this nub (fits perfectly), the rail clip gets a M5 thread (inner thread), so does the part of the adjustment piece with the hex key hole(outer thread). There you go...