Very high quality. Feels like silicone. I should have taken my spa apart before I ordered. My old heater gasket was ribbed on one side with a groove in the union to accept the rib. This gasket is flat on both sides for unions that are flat on both sides. This company sells both types of gaskets. If I had to do it again, I would get the correct gasket. But it works fine anyway. Five stars for sure. Also, heater gaskets and pump O-rings are two completely different things. I don't know why they don't use the same union for both, but they don't.
Rating: [5 of 5 Stars!]