The MagnetoSpeed Sporter chronograph kit was designed to be used on barrels from .5" up to an 1" in diameter. It can also accommodate muzzle brakes, flash hiders, etc. up to 2.7 inches in length. Ideal for contoured rifle barrels (sporter barrels) and long-barreled revolvers. The MagnetoSpeed chronographs use ground breaking electromagnetic sensors, instead of problematic optical sensors, to eliminate common chronograph problems. They are easy to setup, impervious to light conditions, do not blow over from wind and can fit into your range bag. The MagnetoSpeed Sporter is the hassle free way to measure the velocity of your next hunting or target round.