The Siemens 5SL5150-6CC is a 1-pole miniature circuit breaker rated for 125 V DC with a 10 kA interrupting capacity and a B50 trip characteristic.
The 1-pole width (roughly 18 mm per pole on this series) keeps the footprint tight for a DC branch circuit. Wire termination is screw-clamp, typical for the 5SL family — torque to the spec on the side label.
