for anyone having trouble trying to screw on those stubborn new prop nuts this is a great tool to have. i bought a set about 7 years ago when i was building nitro rc cars, and they've lasted. i have even used them to do repaires around the house. they sell replacement nylon pads for it, but i've haven't had to replace them. 

Lol I need that. I was making repairs in my bathroom today and had to wrap mine in heatshrink not to scratch stuff... Not the best solution

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Ah and about new prop nuts - just get a long M5 nut, grab it with pliers and start to screw/unscrew to work nylon inserts a bit