Imichabod has it correct. I went throught the exact same thing, trying to check air pressures in the inside duals and had a heck of a time. I went and bought the one piece steel extender, made checking easier but a day later I had two flat inside dual tires! Not Good. Could not get them to stop leaking. Went and purchased on line the new valve stems that are built with quality, and made the checking and adding of air a snap. Tire Man out of California was easy to deal with, sent the stems quickly and I took the rig to Discount Tire for the install. No more leaks, and I'm very pleased with the stems.