This standoff is 8mm in diameter to allow a skate wheel (with an 8mm bearing installed) to slide on. The wheel is held on one end with the built-in flange on the standoff. The washer and screw hold the wheel from moving in the other direction. The 6-32 threads of the flanged end allow you to fasten the standoff to any #6 thru-hole (0.14” diameter) with a 6-32 screw. For use-cases where the standoff needs to be fastened so that it is concentric with the ½” hole of Actobotics Channel, consider pairing with our ½” - #6 Hole Reducers.