CNC machined RTS Borg Warner steel mini spools replace the side and spider gears in your factory open differential carrier and lock your axles together for positive traction, making them perfect for Circle Track and Drag Racing. RTS-MS-BW-28-4 & RTS-MS-BW-31-4 suits: Ford Falcon ED, EF, EL & AU. Holden Commodore VN, VP, VR, VS, VL Turbo & V8, & VT 6cyl.