A spool is essential equipment for every competition vehicle. A summers Brothers spool reduces driveline breakage by eliminating the differential's fragile spider gears and its weak cast iron case. In addition, a pool improves performance by locking together the axles to provide a constant flow of torque to both drive wheels. For weight-conscious racers, a spool can save up to 20 pounds of unsprung weight over a positraction differential. Summers Brothers spools are made from tough chrome moly steel, and are virtually maintenance-free.