The Reliance Controls PK-Series Power Inlet Box is designed to help facilitate the connection of a back-up power source to a home. Suitable for installation into a 2 ½” knockout on most indoor or outdoor Panel/Link transfer panels or load centers (excludes TCA, TRB outdoor, as well as TRH, TRK, XRH, AND XRK models). Features a spring-loaded, weatherproof cover. 20A - 125/250V, Suitable for outdoor use - NEMA 3R Rated, cULus Listed