Accurate up to 14,000 RPM. Used for 2 or 4 cycle engines, all ignition systems. Protective sleeve withstands high temps (1200 degrees F). Available with 10, 20, 30, 40, or 50 feet (Standard lead length is 4 feet). Bright flash at all speeds The original battery powered timing light, built with quality to last. There is no need to connect to a 12 volt battery for power. This unit is powered by two "D" cell flashlight batteries. Great tool for marine, snowmobile, industrial, racing engines and other small engine timing. Also the batteries are included. Don't accept a copy.