This clamp fits into the slot of many extruded aluminium guide rails, such as the Festool FS and Makita guide rail system. Check your guide rail prior to ordering. The spigot is 12mm wide by 7.4 mm thick and 60 mm long. The ratchet handle results in extremely fast set-up. Once tightened, the grip is rock solid and unaffected by the vibration from power tools.