they are a metric rivet but converts to a 5/32 rivet .....i have a sample set of the stock semi hollow stainless ones that where used but i have not got around to testing them yet ....this i do know they are a pain to put in ......and the stock ones are a pain to remove too ......... when i redid my oval racing phazer i put it back together with the older style solid aluminum ones used on the 70's sleds ....i just added a few extra 3/16'' steal pop rivets in a few key places