These scopes were designed specifically for the 17 Hornady Magnum Rimfire (HMR) cartridge and use trajectory compensation technology similar to that found in military and tactical scopes. The elevation drum increments are precisely calculated to compensate for the drop of 17 HMR ammunition, but will work great for any flat shooting cartridge. Waterproof, fogproof and shockproof. Covered by the BSA Limited Lifetime Warranty.