The MRCOOL MHK20U Universal Air Handler Heat Strip with Circuit Breaker is a supplemental electric heating accessory designed to provide additional heating capacity for compatible air handler systems. It works by converting electrical energy into heat through resistance heating elements, while the integrated circuit breaker helps protect the electrical circuit from overloads. https://www.partshnc.com/mrcool-20-kw-universal-air-handler-heat-strip-with-circuit-breaker-mhk20u