Hour meter keeps track of important maintenance times for oil changes, valve adjustments, spark plugs and moreUsable with any gas engineRecords and displays up to 9,999.9 hours hours automatically roll overIncludes log book to note oil changes, service intervals, etc.Peel and stick or attach with supplied hardwareConnects to spark plug wire, so no batteries are neededSafely and completely encased in 100% epoxyHour/tach meter adds the ability to check engine rpm works with any gas engine up to two cylinders at speeds up to 20,000 rpmFiring pattern: 1 spark = 1 rpm resolution in 10-rpm incrementsMade in the U.S.A.