The Mason & Hamlin Tuning Wrench is primarily designed to be able to tune the unique tuning screws on the Mason & Hamlin screw stringer pianos. These can be found on certain Mason & Hamlin upright and grand pianos. Another way this tool can be used is to be able to adjust the letoff regulating screw on some modern grand pianos without removing the action. The tool is 4-1/2" long and is chrome plated. Quality tool made in the USA by AMS Piano Tools.