Excuse me, are you sure you mean M4 ? Don't you by any chance mean 4mm hex key ?
but that would be an M5 thread. I am looking for replacement bolts for my stem and these could be what I am looking for, I suppose they are probably M5 and not M4, I have not seen any M4 screws in a stem so far. But of course, I can be wrong, I apologise for taking your time if that is the case. Thank you very much, Kind Regards