ProChrono LTD Ballistic Chronograph is great for firearms, shotguns, archery, airguns, and paintball. A chronograph lets you measure the speed that the bullet leaves the barrel. Everything is included for outdoor use. For indoor use, purchase the optional Indoor Lighting System (part# CEI-4100). Requires one 9 volt alkaline battery for operation (not included). Internal and external refinements with updates to the circuitry and enclosure design Built in full featured operating system with multiple shot string memory and statistics Sensing system compatible with a wide variety of light conditions and projectiles Faster internal shot clock for improved accuracy to +/- .5% or better Made in the USA quality at an affordable price Two year warrantee against defects in material and workmanship, and a 1/2 price repair guarantee Over 30 years of experience in chronograph design and manufacturing Replaceable Alkaline 9 volt battery power (not included) for 20+ hours of operation Quality accessories and replacement parts at a reasonable price Made in USA with real service and support