You will have to measure the original O-rings, they are not metric unless they are made to an oddball dimension. Thickness of the large O-ring is 0.210" or 5.334mm not found in any metric listing. Or maybe Febi Bistein is supplying foot and finger O-rings instead of the oddball metric size? The -320 I.D. and O.D. matches the new O-rings in the box. Can you spot the difference between these two?
Silicone is made in only a few durometers and it unlikely Porsche is going to have special special material mixed just for their lowest price vehicle.
Silicone is not the best material for this job as it is not recommended for "most petroleum fluids" by Parker. Included in one box of the Febi tubes was a black small O-ring which usually indicates Buna-N which is recommended for petroleum fluids.
O-rings from McMaster come from USA Sealing and show batch and cure numbers on the package.
