M12 X 1.25 die. Works great for cleaning up the threads on wheel studs on Datsun vehicles. Has hex shape for using a wrench or socket to thread on. Datsun 240Z, 260Z, 280Z and 280ZX 1970-83 use M12 X 1.25 threads for the wheel studs from factory.
Correct thread size for the mustache bar bolts that come out fo the body as well.