This 12 volt Gast vacuum pump is for vehicles using engine combinations that provide little or no manifold vacuum required for braking. When vacuum drops below 15 in/hgof vacuum, the vacuum switchactivates the vacuum pump and increases the brake vacuum level to 22 in/hgof vacuum.The compact, lightweight 22D Series offers oil-less operation and is well suited for noise sensitive environments. It can be mounted in any plane and has a durable design, which contributes to its flexibility and long service life. Additionally, the unit requires minimal power and can be used as a compressor or vacuum pump for maximum versatility.