Many of the newer boats have the thru-hulls that are made of marelon. On our 310 the handle snapped off while closing. As I said before, hearing water rush in is not a good sound. I have talked with Randy at Forespar, and although they were not happy about one of their products failing, they are an absolute pleasure to deal with. They have sent a replacement, free of charge as the boat is less than a year old. In the FYI category: I asket if you could replace the body of the valve with any other type, and on the integrated valves you can not. The threads will not match. They have made a change in the body to strengthen it by adding a long screw that goes through the handle and into the body of the valve. If you want to replace your current valves with the stronger one they are about $40 each.