Hornady Critical Duty 9mm Luger Handgun Ammo - The FlexLock design incorporates two important features that make the Flexlock handgun ammo unique. The Flextip is made of a rubber like material to prevent mashing of the bullet tip when it comes in contact with hard materials and barriers. It also prevents clogging, which aids in consistent expansion. The Interlock band that wraps around the midsection of the bullet assists in weight retention and expansion. FLEXLOCK bullet Cannelured bullet with crimped case Interlock band Nickel-plated cases