https://apollovalves.com/article/pex-a-b-or-c-understanding-the-differences Had a plumber come out to my sisters house cause it was just to much for me to fuck with. He replaced with this and said it could expand to twice its size in a freeze. Thinking of having the whole house re plumbed with it ( small house). Npw at work we have one line with pex ( not sure what type) but I have had to fix two leaks when not freezing. Of course it could have been fuckin moles chewing on them.