APC Slow-Fly Electric Series props offer high thrust at low RPM, and offer great value for your electric powered models. The Slow Fly Pusher Series are designed to be used in matched pairs with twin engine models, or for use on the new Quad-Rotor models that are becoming so popular. The center hole of the prop is designed to accept a reducing bushing to fit your propeller shaft. Included with the prop are 2 bushings to fit 5mm (3/16") and 6mm prop shafts.
According to the widely accepted Maximum RPM formula of 65,000/D for APC SF-Series props, the 12x3.8SF pusher prop should not be used over 5417 RPM.