Bronze pre-load nut prevents back driving due to vibration. This exclusive design eliminates the constant adjustment required on other lifts * Direct drive lead screw is fast-acting and self-cleaning. Won"t get sloppy over time like belts, chains and gears * Twin ball bearings support the weight of the router. Most other lifts use cheap sleeves * Ultra-flat cast iron plate is precision-ground and measures 8-1/4-Inch by 11-3/4-Inch. Fits all Bench Dog router tables. Various size plastic insert rings are sold separately (1 included) * Use 40-002 ProLift adapter for Bosch 1617/1618, DeWalt 610,616/618 and Porter Cable 690/890 routers. Use 40-003 adapter for Makita RF1100/1101. Adapters sold separately