This is a new MagnetoSpeed V3 barrel-mounted ballistic chronograph. It measures true muzzle velocity with up to 99.9% accuracy. The device is compact, portable, and includes a battery. It's designed for rifles, long-barreled revolvers, rimfire, and shotguns, fitting barrel diameters from 0.5"-2.0". Asking $175. I also included is another almost complete kit. The bayonet in the second kit doesn’t work sometimes.