Hornday Bore Driver Muzzleloading Bullets feature a polymer base (not a sabot) that seals the bore for maximum energy transfer and accuracy. The FTX bullet features a rugged gliding metal jacket coupled with patented FlexTip technology and an InterLock ring that deliver maximum lethality. The polymer base features a post that fits into the bottom of the bullet that swells in diameter at ignition for better torque engagement.