MagnetoSpeed Sporter Barrel Mounted Ballistic Chronograph, for Barrels from 0.5in up to 1in MSSP 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 screwdriver to swap batteries Three sensitivity settings for fine-tuning Integral 3.5 foot sensor cord