GEMFAN 9x4.5 Nylon Propeller for Electric (2pcs) Specifications: Bore diameter: 6mm Hub thickness: 11mm Adaptor ring diameters: 3mm/ 3.17mm/ 4mm/ 5mm/ 6mm/ 8mm Weight: 21g (each) Includes/Requires: Includes: 2 x propellers 2 x adaptor ring sets * Both the propellers are same type, NOT CW/CCW pair.