I bought this tank cap to replace the original cap gasket on my 2.5 gallon HF pressure tank. This gasket was the exact size for an HF pot. It was a little thicker than the original seal, which was great. TIP: It might not matter, but I made alignment marks on my tank and lid to align them every time I use the pot. I can finally cast pen blanks again without losing pressure. After installing the gasket, I tested the tank at 30psi for 24 hours with no leaks. Highly recommend this seal from TCP Global if you are replacing an old seal.