Does anyone know recommend inside and outside diameter off fuel tube? Serpent seem to use 2mm/5mm but wondered if it is really larger. I tried measuring it but it stretches

There are tubes with an inside diameter up to 3mm. You can notice the difference but I think only the 2mm is to small. 2.3 and higher seems to be OK. Outside diameter does noet matter, the thicker it is the stiffer it is.

Thank you sir... I have noticed some are very hard to get onto my Novarossi pipe and almost need to warm them up in hot water to get it over a bit like a garden hose

Thanks again for reply

Andrew