Interesting question, R134 will go through any normal “rubber” pipe it would need to be the proper air con rated stuff as there is a barrier built into its construction that stops the gas getting out, ideally it also wants to be clamped onto the pipe using proper crimpers and couplers, anything else will be a waste of cash as your refrigerant will go quite quickly :blink: scrap yard may be better got a few pipes for around the £10 mark. best of luck