GWS HD-9075 9x7.5 Hyperdrive Propeller GWS Hyper-Drive series props offer high efficiency and great value for your electric powered models. The Hyper-Drive series of prop have extra reinforcement in the hub area, which allows them to be run at higher RPM than the standard Direct Drive series props. The center hole of the prop is designed for a 3mm shaft, and can be drilled out for a 1/8" (3.17mm), 4mm or 5mm shaft. According to the widely accepted Maximum RPM formula of 120,000/D for GWS HD series props, the 10x8 HD prop should not be used over 12,000 RPM.