Ive got a 10″ orbital that I use…. but am thinking of adding a 7″ specifically for the boat… the 10″ is great for most of the hull… but the areas around the decks, consoles and transom would be better done with the smaller head. Catman is right I think I paid $20 for the 10″ (Turtle Wax brand)… and the 7″ is a little less…