- The capillary depth gauge on this pressure gauge had dried up, discolored, and shrunk. Thinking it was just tubing I could buy locally, I pretty much wrecked the old tube trying to get the plug out. I finally found the correct sized tubing online thru U.S. Plastic. It's 5/32" Outside diameter and 3/32" inside diameter... Fits in the groove perfectly. I made a new plug by mixing JB Weld and then sucking a little into the end like a straw. It SHOULD work as well as the original. These things were never all that easy to read but I'm at least glad to restore the appearance. The pressure gauge works perfectly.