Originally Posted by Andrew R Stewart

If the question is what is the axle's through hole, that positions the QR skewer, than I would speculate it's slightly bigger than 5mm to allow for a bit of clearance. I also suspect that different axle manufacturers will have their axle "holes" a tad different but all close to the same dimension. Of course one could measure and then we would not have to wonder which aspect was in question, or what the dimension actually is. Andy