Continuing in our tradition of bringing innovation to the muzzleloading industry, we redesigned our breech plugs to better accommodate today's modern black powders. The fixed vent breech plug provides 40% longer life and drastically less blowback. Now you can shoot more and clean less! 0675-0285: Fits: Original DISC? (Uses Orange DISC? primers). Hex Head. 0675-1156:Vent liner is fixed and non-removable. Fits: W209, TK2000, USAK, MK, LK, BK, BH, and LH. 0675-1157: Fits: DISC Extreme, Vision, LRH, MH, Elite, and KP1.