The Rheem-Ruud 42-105601-25 SPST Pressure Switch -0.35" WC is a single-pole, single-throw pressure switch engineered for gas-fired furnaces and heating systems. Rated at -0.35" WC, it monitors negative air pressure within the draft inducer to confirm proper venting before ignition. Once the required pressure is detected, the switch closes to permit burner operation. Used in Rheem and ... https://www.partshnc.com/35wc-spst-pressure-switch-3