To my dismay, these 3/4" 4-way unions arrived today and did not fit 3/4" Pex Pipe. How stupid can the manufacturer of these be. So, I am sending them back and ordered the 5/8" 4-way union, because it seems that is what I will need to fit into the 3/4" pex pipe hole. This is not a water project, so I am not worried about a super tight fit, but for a game that I am devising for my game rental business. I wish that I would have read the review comments first. So, if you have 3/4 Pex that has a 5/8" opening, then buy the 5/8" 4-way union or you will be not a happy camper when the 3/4 4-way arrives which is too big. Ugh.