"This MidNite Solar photovoltaic DC circuit breaker is a dinrail mount breaker that is specifically designed for photovoltaic combiners. Provides branch circuit protection for DC loads and is suitable for charge controller input and output disconnects. Accessory Type DC circuit breaker, Compatible With Photovoltaic combiner, Dimensions L x W x H in. 4 1/2 x 1/2 x 3 5/16, Mount Type Dinrail mount, Amps 30, Class Rating Meets NEC requirements. Meets NEC requirements for over current protection on both sides of charge controllers to protect wiring from potential fires in the event of controller failure Can also work as on-off switch for DC load circuits"