I wish I could only have bought one of these, but they were only sold in pairs so now I have a backup.  The hubs are easy to put on, except they take 2 special axle nuts per axle.  Each round nut has 4 slots and needs a special tool to tighten (torque).  I had zero luck trying to find rebuild kits for this hub.  If they exist they might have been cheaper.  The last hub I had got ruined from loose axle nuts.