The ABB S201P-B16 is a 1-pole miniature circuit breaker (MCB) rated 16 A with a trip curve B characteristic, for 277 VAC circuits. The B curve means it trips between 3x and 5x rated current — so at roughly 48 A to 80 A fault current — which makes it a good fit for resistive or lightly inductive loads like lighting, heating, or control transformers where inrush is low.
Snaps onto standard DIN rail — the same footprint as every other S200-series MCB — so it drops into an existing distribution board or sub-panel without extra bracketry. Single-pole format means it occupies one module width, leaving the rest of the rail for additional poles or other devices.