This is Federal 223 Remington 42 Grain BallistiClean Lead Free Frangible Ammo.
Recommended for indoor ranges, Federal BallistiClean RHT is lead-free ammunition featuring a Toxic-Metal Free primer. The frangible bullet, formed from powdered copper, is designed to crumble into small fragments when it hits a steel backstop. This reduces the ""bounce back"" hazard and eliminates airborne lead and barrel fouling. This product is sold 20 rounds per box.