The Weil McLain 511-624-521 SPST Pressure Switch 1.25" WC is a genuine replacement pressure switch designed to monitor air pressure and verify proper venting in compatible Weil-McLain gas-fired boilers and heating equipment. It works by sensing the required pressure level and activating or interrupting the electrical circuit to ensure safe burner operation. T https://www.partshnc.com/125wc-spst-pressure-switch-2