STOCK UP and SAVE! Go to my store or “sellers other items” and type in “muzzleloader” to see more! New AFTERMARKET Thompson Center 15/16 Flintlock Breech Plug. Has 5/8-18 threads. Will NOT fit Thompson Center factory barrels. These are for blanks or drop-in barrels by other manufacturers. They’re slightly oversized so you can file/mill to your barrel and will need the touch hole located. We pride ourselves in offering a variety of quality production, custom and aftermarket replacement parts and supplies for black powder builders, shooters and enthusiasts of any level.