Metra Tire Double Seal Inflate Through Valve Stem Extension Caps, Inflate Thru Wheel Tire Cap, Semi Truck RV Bus Car (50 Pieces) The original Metra Tire double seal valve stem caps designed for heavy duty and high efficiency use. Gauge and inflate valve extensions directly through the cap. Inflate tires through these caps without unscrewing them. Save time and labor by eliminating the need to remove caps to check and inflate tire pressure. Valve has two seals and is protected by a solid, all metal housing with a durable, high-temperature-resistant rubber o-ring inside. Safety feature causes seal to tighten to prevent air loss in case the valve fails. Caps are grooved for use by various lock-on chucks and inflation devices. Grooves are threaded so you can even screw other caps onto them. Hand tighten only. Length: 7/8". Seal rated for -40F to 250F.