I'm using PEX,
I was referring to IPEX as a brand.. the PEX fittings I have were manufactured by the company IPEX. They are standard PEX with F1807 stamped on them.
They are not for the IPEX Aqua or other systems.
I've been told by the Vanguard guy not to mix their Vanex PEX line with other brand of PEX fittings because the crimp will end up too tight.. for example go out to home depot and get some PEX fittings, according to him it's not good, they must be Vanguard brand.. It doesn't make any sense to me.. they all look the same and have the same F1807 stamped on them.
I've read posts of people mixing four different brands of PEX within a system without problems.