Needed to replace the hub on an OLD tandem boat trailer. Figured it would be an easy replacement but not so. 1 inch spindle size and it is 4.25 inches long with 1.25 inches of that being the threads. Old hub and replacement hub are the same length (4 in). New hub fits the spindle but doesn't leave enough thread out to put the nut on. Turned out that the inside bearing on the old hub is recessed into the hub considerably more, as is the outer bearing! They are only 2 inches apart inside the hub and this allows the splidle to be sticking out far enough to be threaded. No trailer store knows anything about this. Only ID on the hub is 58000. Bearings are the same! This trailer has no axles, just spindles.