These 100 Counts 0.68 Cal Hard Nylon Balls Are Great For Self Defense. They Fit Perfectly For Umarex T4E HDR68/ HDS68/HDX68/ HDB68 and Byrna Series(SD/LE/EP). They Can Also Be Used For Paintball Training And Target Practice. Solid, Hard, Smooth, Polished And Seamless. Will Never Get Jamed. These Plastic Kinetic Rounds Fly Straight And Hit Hard. Very Accurate Shooting From A Long Range. As Heavy As 3.6 Grams Of Each Round. Definitely A Glass Breaker With High Impact and Best Penetration. No Rust Or Scratches, No Deforms Or Flaws. Bright Neon Yellow And Red Color Make Them Super Easy To Find In Your Yard. They Can Be Reused For A Long Time.