The MagnetoSpeed Sporter chronograph was designed to be used on barrels from 1/2 inch up to 1 inch in diameter. In can also accommodate muzzle brakes and flash hiders up to 2.7 inches in length. Ideal for contoured rifle barrels (sporter barrels) and long-barreled revolvers. - For center-fire rifles and revolvers only not compatible with airguns or rim-fire. (Note: Not compatible with the Large Brake Adapter or the V3 Rail Adapter.) - MagnetoSpeed Sporter features : - Simple one-button cycling display (shows recent shot velocity and statistics plug in to turn on) - Battery : 9-Volt (included) - Easy access battery compartment no need for a screwdriver to swap batteries - Three sensitivity settings for fine-tuning - Integral quick-attach strapping system; with metal buckle and triad thumb nut - Proven technology with updated sensor design - Integral 3.5 foot sensor cord - Kit includes: - Display Unit - Bayonet-style sensor (Bayo) - Thick and thin rubber V-block spacers - Heavy duty strap with thumb nut tightener - Ultra-compact storage container.