Prop Savers help prevent propeller and motor shaft damage in the event of a prop strike.
This Prop Saver has long screws which secure the prop saver to the motor shaft and also act as anchors to the included o-ring to hold the propeller in place.
Most GWS 2 blade slow fly props and APC slow fly props fit this prop saver. Be sure to use the correct prop insert provided with the APC props.
If your motor has a long shaft, I recommend that you mount the Prop Saver close to the motor and cut the motor shaft even with the Prop Saver. This allows for maximum flexibility for the prop in case of a prop strike, and helps prevent bending the motor shaft.
If you allow the prop shaft to extend through the prop hub, most any prop with a 3mm hole can be mounted, but the Prop Saver does not protect the prop very much, as the prop cannot flex in all directions.