I don't have a sample marked in mm to try, but 7/16 " works fine.  3/8
would be too tight.  I suspect that the nominal metric size is 11 mm.
Note that this should be hose chemically suitable for gasoline, but
need not be high pressure "fuel injection" type on the input side of
the pump.

Larry A.

On Sat, Sep 29, 2012 at 3:02 PM, Robert Mac Dowell
<yakandhike@comcast.net> wrote:
> My 84 westy has a bosch fuel pump on it. Does anybody know what size the fuel hose is on the fuel tank side. Its only about an inch and a half long but the diameter looks like about 3/8. I'm guessing at 8 or 9 mm in metric. And is it the same size on both ends. I have the square filter on the other end. This hose goes between the filter and the pump.