I have a 2016 Sprinter Sportsmobile. Shortly after taking delivery, I had installed a set of metal extended valve stems from the Tire Man (
Tire-Man: Products). I have been very satisfied with the kit, but I recently had a slow leak develop. After some time trying to find the leak, I have concluded that it is likely where the valve stem enters the wheel. There is a small gasket/grommet on the inside of the tire. Before I take the van into the tire installer to have the wheel pulled, I thought it prudent to try to get a replacement gasket in case it has to be replaced. When I tried to contact the Tire Man, I learned that he is out of business, although the webpage is still live. It now appears that if you want steel extended valves for Sprinter duallies, the only source is this:
Duallyvalve Kits for Class B or C - Sprinter Trucks. They sell gasket/grommets that they claim will fit the Tire Man valve stems, and I have some on order. I'll report back with the results.