I have a fuel connector kit for my Eberspacher S2 Airtronic but the fuel hose is way too small. Looks like it needs an internal diameter of 9.5? What do you recommend ?

An S2 Eberspacher Airtronic should typically use fuel line ( blue ) with dimension specification below

4mm  = external diameter

2mm =  internal diameter

1mm  = wall thickness

The connector hoses ( black in image) when used to connect the blue fuel pipe typically have dimensions

9.5mm  = Outer diameter (not critical - sometimes larger depending whether marine grade)

3.5mm = internal diameter

3.0mm wall thickness

Hope the above helps. Please email sales@butlertechnik.com should you have further questions

Thank you