Connects to all four tire valve stems at the same time and immediately begins to equalize the pressure in all four tires. Gauge shows air pressure. Open the included ball valve and reduce the pressure in all four tires. Attach a compressed air source to the quick disconnect and inflate all four tires at once. While inflating or deflating you can close the ball valve to check the tire pressure at any time. 55 psi max. Higher pressure systems available. The Large Wheelbase system will put the manifold between the drivers seat and door on a Full Size Pickup (Super Cab) and will reach all 4 tires at the same time. The four hose lengths are 9', 9', 16', 16'. Longer hoses available at 0.50/ft, contact us. This is not something cobbled together from Harbor Freight junk like other systems that you may find.