3.5x2mm OEM VW CRP black cloth-braided fuel line, as used in most VWs. Also serves as an excellent vacuum line.
Sold by the foot.
Mk4 TDIs require approximately 10′ of this hose; Mk3 and B4 TDIs require approximately 7′.
We also offer a complete vacuum and fuel hose replacement kit for Mk4 TDIs here.