As has been suggested, if you lose your Propeller nuts, M6 will fit nicely. Today I had a original nut come off, so I got a box of M6 nuts with the nylon at the top, these lock nice and tight and will not come off like the original, the best and cheapest investment yet, better than using lock tight. I tired a washer underneath, but there is not a lot of thread to play with and think this is also why they come off. Tightened the nut without washer and locks nice and tight in the nylon thread, so these will not come off. The first thing to do is throw away those original nuts and replace them, like I did, much better and safer. Don't risk lock tight, it eats plastic. my solution is much better, and neater.