Prop Saver Size Shaft Prop Saver 3mm 3mm Prop Saver 3.2mm 3.2mm CNC machined aluminum Prop Savers, for parkflyers only. Good for model airplanes up to 12 oz. (345g) or 100W of power and APC Slo Flyer propellers. No need for prop shaft adapter, all you do is install this little Prop Saver on your motor shaft and attach the propeller with included rubber bands. No more broken props after those not so perfect landings.