This ammo is for cartridge size .44 Special. The bullet is made from Copper. The diameter (caliber) of this bullet is 0.429. This bullet weighs 125 grains. This bullet leaves the barrel at 1250 feet per second. The ammo case is made from Nickel Plated Brass. This ammo is a proven round for hunting. The bullet in this product does NOT contain lead. This round is designed to be supersonic and travels faster than the speed of sound. The muzzle energy of this ammo is 434 ft lbs. This product has been designed to be an effective choice for the ultimate in self-defense applications. The bullet in this product has a Sectional Density, (SD) of 0.0970280690560411. SD is the ratio of an object's mass to its cross sectional area with respect to a given axis. It conveys how well an object's mass is distributed (by its shape) to overcome resistance along that axis. This ammo IS SAFE to use in a suppressor. The bullet in this ammo has a ballistic coefficient (G1) of - Generally, the higher the coefficient, the more stable the projectile will be in flight. Each box of ammo contains 20 loaded pieces of ammunition. This ammo is manufactured by Underwood Ammo