Sizing Guide for vacuum hose fittings
Sizing Guide
Here are suggested fitting / vacuum hose pairings. These particular pairings are suggested to keep the restriction caused by the fitting to a minimum. As a consequence you may have to expend some effort to get the hose on to the fitting, but vacuum hose is rather forgiving in that regard so with a little water or alcohol used as a lubricant you should be able to twist the vacuum hose on to the suggested fitting size.
2mm vacuum hose -> use 1/8 fitting
3mm vacuum hose -> use 5/32 fitting
3.5mm vacuum hose -> use 3/16 fitting
4mm vacuum hose -> use 3/16 fitting
5mm vacuum hose -> use 1/4 fitting
6mm vacuum hose -> use 5/16 fitting
8mm vacuum hose -> use 3/8 fitting