PATENT PENDING. The XL [extended length] is for wheels with a deeper valve stem well, such as some beadlock wheels.TYPES OF USAGE -Connect to large shop compressor. At 120psi and 10 CFM you can expect sub 10 sec air up time for 37-39 tires. Use high flow fittings and inflators for best results.Onboard air. Inflation times will depend on CFM of compressor and psi. Because there is little to no pressure drop across the Schrader valve, the work the compresser has to do is greatly reduced. This will result in fast inflation times as well as longer compressor life. Heat produced by the compressor is also greatly reduced so duty cycle increases. Due to lower CFM of onboard air compressors smaller fill lines may be used. 0.188 ID is the smallest that should be used.Auto shut-off. By using an air regulator and setting to the desired pressure, the compressor will shut off when desired set pressure is met. This will reduce inflation speed a little depending on compressor used. 10-20% longer time. The ability of not having to monitor pressure is a nice convenience.NOTE: If not using the auto shut-off ability of the valve, you can use a gauge on the opposite valve to monitor inflation pressure.