This shaft is a replacement shaft for some older PG Series Gearboxes. If your existing gearbox shaft has been damaged from the intensity of robotic competitions, you might not need to replace an entire gearbox, but just the shaft. The PG series gearboxes have a few different shaft styles. Some have the shaft welded to a plate, some are shafts are hex. Be sure your gearbox is a non welded, non hex version before ordering this replacement shaft.