Square SP104BT8X BT8 Spindle & 4-4" Bolt Circle Trailer Hub. 4 studs 4" Bolt circle using L44643 inner and outer bearing hub. (BT8 Spindle 1in.). Hubs are pre-raced & pre-studded with 1/2"-20 studs. Includes Hub, inner bearing, outer bearing, seal, grease cap & lug nuts. BT8 Spindle, Spindle base size=1 1/4" Spindle length=3 3/8" Overall length =8 1/4" Capacity (pair) 2,000 lbs.