This part of ISO 12164 specifies dimensions for hollow taper shanks with flange contact surface (HSK) to be applied to machine tools (e.g. turning machines, drilling machines, milling machines and grinding machines). A range of shank sizes is specified. This part of ISO 12164 specifies two styles of shanks. Style A incorporates a grooved flange to enable automatic tool exchange. The tools may also be exchanged manually. Style C has no groove in its flange and can only be manually exchanged. Provision is made for manual clamping of both styles via a hole in the shank taper. The torque is transmitted at the tail end of the shank through keys as well as friction.