Hornady Superformance Shotgun slugs feature the innovative, accurate and deep penetrating MonoFlex projectile in your choice of either 12 or 20 gauge loads; At the heart of the Superformance Shotgun slug is the MonoFlex - a monolithic solid projectile made from copper alloy (95% copper / 5% zinc); The MonoFlex won't separate, and retains 95% of its original weight; The Superformance Shotgun Slug is built to deliver maximum velocity for flatter trajectories and enhanced terminal performance