First comment is that I have never held these hubs in my hands and so have no real idea how to service them. However, the free hub is very likely NOT a Shimano part. People don't design bicycle equipment incorporating spare parts from other manufacturers. Second, if there are 5 mm Allen slots on both sides of the hub it is VERY likely that is how the thing comes apart. You will most likely need to apply significant force on the wrenches. It is even possible that thread lock compound was used during assembly.Velocity standard rear road hub. Need to swap out freehub due to the fact that the gears moved into the splines. First question: is this freehub likely a Shimano part or would this be a Shimano 'type'? possibly in aluminum? Next, I'm thinking that what holds this freehub on is probably a stub axle. In reading Sheldon Brown I got impression this would be standard thread (counter clockwise to remove). So I tried to unthread using two 5mm allen wrenches in the ends of the axles. It hasn't come easily and I'm hesitant to up the ante. Am I missing something.