Buttstock Flex Loader, 50/45Cal Description A butt stock version of T/C s Flex Loader, allowing the hunter the opportunity to carry three complete charges (pellets and sabot) strapped to his muzzleloader for instant access. Made of Bio-Flex a special silicone material that will stay pliable in the most frigid condition. Houses four 209 primers; instantly accessible. Laces on butt stock securely. Bio-Flex material grabs and almost sticks to surface of butt stock.