HBSM20H - Allows calipers with I.S. mount to be converted to fit Post Mount forks - you will also need a 20mm bigger disc rotor when using this mount. HBIS20 - Allows calipers with I.S. mount to run a 20mm bigger rotor on forks with I.S mounts - you will also need a 20mm biger disc rotor when using this mount. **Please note: these mounts are not suitable for Post Mount type calipers**