This is the Great Planes ElectriFly 3.0mm - 5mm Prop Adapter with Set Screw and Propeller Nut.
FEATURES: Compatible with any electric flight motor having a 3mm diameter shaft Mounts onto the shaft coming out of the gearbox or motor with the included set screw. The propeller mounts onto this with the included nut Aluminum prop drive Metal hardware One year quality guarantee Fits a 3mm motor shaft with a 5mm prop shaft
INCLUDES: One Prop Adapter One 3.5x5mm Set Screw One 5/16 Propeller Nut
REQUIRES: Installation onto the motor or gearbox shaft
SPECS: Length: 1.1" (28.9mm) end to end .69" (17.6mm) complete shaft w/.45" (11.3mm) threaded portion.