For dependable operation of air-pressure warning systems. Sealed contact design prevents short circuits caused by moisture and contaminants. Normally On (contacts open at rising pressure at 55-65 psi) In trucking, unit of measurement for tire air pressure, air brake system pressure and turbocharger boost. (379 - 448 kPa). 1`/4"-18 dryseal thread mounting stem, 15/32" long. Insulated. 8-32 screw terminal.