I have an RV that has 1/2" that has type of plastic water line. It is not CPVC, I want to say Pex tubing. I want to install a Culligan water filter that has a 1/4" line. I need a "T" that will fit both lines. The fitting is not glued on, nor put on with a metal band compressed around it. The lines just slide in, but not out. I think its called a "Quest" fitting or something. My question is what is it called, and where do I find it?