The Shimano Crank Tool (SCT for short) is specifically built to service the chainring lockring on Shimano single ring cranksets for 12 speed drivetrains. It features a large hex that can be used with a 1. 5" or 38mm wrench or locked into a vise. The clearance hole is kept to a minimum to keep the tool engaged on the low profile lockring, minimizing the chance of damaging the tool or parts.