polyamide tubing

[POLAND_SPUD]

have a look at this http://www.allegro.pl/show_item.php?item=677854800

4 mm size has working pressure of 32 bar and burst pressure of 130 bar (at circa 20 degree Celsius)

I have been using this tubing and push-in fittings for pressures of up to 600 psi and it hasn't failed so far

hope you'll find it useful

make sure to ask for polyamide not PU... and remember to ask manufacturer for pressure rating as it may differ due to different material properties and production techniques