APC Thin Electric 7x4 Prop
APC Thin-Electric Series props offer high efficiency and great value for your electric powered models. The center hole of the prop is designed to accept a reducing bushing to fit your propeller shaft. Included with the prop are 5 bushings to fit 3mm, 4mm, 5mm, 6mm and 8mm prop shafts.
According to the widely accepted Maximum RPM formula of 145,000/D for APC E-Series props, the 7x4E prop should not be used over 20,714 RPM.