Having the incorrect tire pressure can be dangerous, especially for semi trucks and other commercial vehicles. The V2B Inflate Thru Valve Cap save time, making it easy to check, inflate or deflate your tires. The V2B is an inflate through sealing valve cap used in place of a standard valve cap. If you have a lot of tires to service, you will love the V2B. Inflate, deflate or gauge directly through the V2b, saving time during inflation and pressure checks. Automatic inflation systems lock right onto the V2B. Seals like a high pressure cap, yet offers the convenience of an inflate through extension. The V2B performs like a check valve - the seal becomes tighter in the event of a core failure. Heat resistant grommets provide additional protection for extended high temperature running. Features tough, all metal housing, precision fit brass components and durable self-sealing O Ring. This is the original inflate through valve cap proven in millions of miles of service by the nation's largest trucking companies. Install the V2B onto the valve, finger tight. Do not use pliers. the V2B is a cap, it does not require an additional cap.