$9 each for a spinner nut is a bit pricy, but not that bad if holds up. I picked up some 5mm nuts from Bill Turner. They are solid, so they can't dent like the Dubro ones can. If the Trueturn ones can be dented, then I think that's a bit much. (fwiw, I use the Durbo ones on my B class planes. I like how they work with my starter and the pretty colors. But I've had to toss 2-3 of them now after caving in the sides in mid-airs).