It's not for protection. The part number of the blade is B2004 for a 48" blade and B2005 for a 60" blade. But to connect the blade to the 3PH you need the main frame B2002. When I bought mine, my dealer told me the price of the blade and the price of the main frame. So yes it's required you have no choice. Usually the main frame is the same price as the blade. For exemple: 200$ for the blade and 200$ for the frame.