The only pex fittings I have used,....and seen on RVs is "flair-it", found at any RV supply, and many hardware stores. They are easy to use, can't leak, and are less expensive than other pex fittings. They are also the standard fitting used in most all MFG'd Homes
Rich
'01 31' Rexall Vision, Generac 5.5k, 1000 watt Honda, PD 9245 conv, 300 watts Solar, 150 watt inv, 2 Cos 6v batts, ammeters, led voltmeters all over the place, KD/sat, 2 Oly Cat heaters w/ ox, and towing a 2012 Liberty, Lowe bass boat, or a Kawi Mule.