"Designed for use with Matco tap and die sets including 124MATDS, 81MATDS, 40MTDS and 40STDS","1/4\" square drive","For areas the ratcheting tap handle won't fit, use with 1/4\" drive tools or drive from the outside hex flats for extreme low profile usage TAP SOCKET #2 1/4" DRIVE TS800-02 | Matco Tools