Long solid metal custom-formed valve stems for inner and outer dual wheels/tires ARE NOT called "extenders". If you ask for "extenders" you will get some kind of extensions that screw onto the stock rubber valve stems. These "extenders" can unscrew and leak air and vibrate with wheel rotation eventually causing the rubber valve stems to crack open and leak air out. Loss of pressure can cause sudden tire failure with flailing steel tire belts damaging propane lines, wiring and holding tanks. Tire Man or Borg products will cost considerably more than cheap "extenders" but will be well worth it to you in peace of mind and when checking tire pressures in five minutes or less with no effort.