the thread on the axle is 8-32 so i orded sum nylon 8-32 nuts from amain , they look like the only nuts that will fit inside. im pretty disapointed with the whole set up to tell ya the truth . if the whole idea is to only be held on by the drive pins then its just stupid . i was gunna email them but cbf . also i had both grub screws come loose and the drive pins fell out .i hate that fact of a lil grub screw holding them in . so i used a M3 cap head bolt insted to hold in the pins. cos of the bigger head you can do them up really tight , no dramas since. i should have bought the AKA set up , wonder if they are held in with nuts or its the same sh%tty set up with the pins.