o.d. is 5/8.....but, i'm sure the other connections don't have the ferrule insert. as far as it being pex or not....it's an older modular home...the water lines are all the black pipe and are continuous runs except where there are t's....there are not elbows where it turns to go to other connections....there's just bends (not sharp)....on the original connections (like at the t's) there are those crimp style connectors like they use on pex.....again, may not be pex, but that's the best way i could describe it so everyone would know kinda what i was talking about. when i fixed the one leak, i stuck one of the sharkbite type connectors on the black pipe coming up thru the floor....then pushed a piece of 1/2 white pex into the other end of the sharkbite.....then, slipped a 5/8" brass sleeve onto the pex and connected it to the shut off valve with a compression nut....didn't use a ferrule insert/didn't have one.....it sealed fine, no leaking.....i'm just worried about, over time, the brass sleeve cutting into the NOW PEX LINE and leaking again in the future.....do you think it's "fine"...or as Jerome2877 states above, will i have more problems in the future and need to change it all out now??? thanks for your input..