Fits 21 mm and 13/16in. spark plugsUltra-strong tool steel constructionSlim skeleton profileUse with a 3/8in. square drive or 17 mm wrenchInnovative internal plug retention systemProtective black oxide coatingEasy to read laser etched markingsCan be used as an axle holding tool on bikes with 17 mm or 24 mm internal hex axlesThrough hole allows use of screwdriver or holding rodLight weightPatent pending