Summitlink 6x CNC Aluminum Self-tightening Nuts w/Wrench for DJI E-series E300 F550 F450 Set of 6 Aluminum Nuts 3x Clockwise 3x Counter Clockwise for DJI E300 Propulsation System These self-tightening locking nuts are required when you want to use a traditional non-self tightening props, such as carbon fiber props. These locking nuts are made of CNC aluminum that is very strong and super light. The quality is much more superior than those plastic aftermarket locking nuts. Get these aluminum locking nuts for top level safty! DJI E-series E300 6x CNC Self-tightening Nuts w/ Wrench for F550 F450 Zenmuse