Hey, I'm currently attempting to fit an oil catch can to my Stilo- the can I've purchased has an external hose diameter of no more than 15mm, but the original hose is bigger than that- something closer to twenty; I have nothing to measure the internal diameter of the original hose- does anyone know this statistic? I'll look for a reducer to bridge the size gap

Thanks!

You should find what you're looking for here:

http://www.advancedfluidsolutions.co.uk/barbed-straight-reducing-connectors-hose-joiners-60-c.asp

Used them when I fitted my OCC...