Spedix Quad Wrench with One-Way Bearings

This handy wrench from Spedix allows you to change M5 prop nuts with minimal effort. The socket rotates in one direction to allow you to continue to tighten or loosen without having to reset your wrench's position. Just crank away until the nut is tight or simply flip it over and use the other side to take a nut off. 

The side arms give you great leverage to rotate the most stubborn locknuts. The arms also have M3 sockets to fit smaller locknuts.