GWS Direct Drive 6x3 Propeller. GWS Direct Drive series props offer high efficiency and great value for your electric powered models. The center hole of the prop is designed for a 3mm shaft, and can be drilled out for a 1/8" (3.17mm) shaft. According to the widely accepted Maximum RPM formula of 100,000/D for GWS DD series props, the 6x3 DD prop should not be used over 16,667 RPM.