Siemens 2P Combination Circuit Breaker/Surge Arrestor. Requires Two Panel Spaces and Provides surge protection for ALL branch circuits in the panel without sacrificing breaker spaces. This device includes two 20A branch circuit breakers AND surge protection all in a two inch wide plug-in device. Two red LED lights "on" indicate surge protection is working. This device is UL listed for use in Murray brand loadcenters and replaces the MSA2020SPD