PropPro "Protection from your Propeller" Protect your family, friends, and pets near your NON-SPINNING boat propeller, in and out of the water. With the easy-on easy-off proprietary retention plates, applying the PropPro to your propeller is a snap. The retention plates are all replaceable and the skag slots double as strap slots in strong current situations. The PropPro fits boat propellers from 10" to 15.5" in diameter, irrespective of pitch or numbers of blades. The PropPro also fits double stacked propellers and covers the outside propeller which is the main strike point of a NON-spinning propeller. ** If you are purchasing a PropPro for a double stack propeller set up, send us a message so we can include the correct length strap.