What this breaker is and where it fits
The ABB S201-K1.6NA is a 2-pole (1P+N) miniature circuit breaker rated at 1.6 A with a Trip Curve K characteristic, for 277 VAC circuits. It interrupts faults up to 6 kA. The DIN-rail mount means it snaps into a standard panel enclosure alongside other System pro M compact devices.
What the ratings mean for your panel
The 1.6 A rating and K-curve are the key specs here. Curve K is a medium-magnetic trip designed for motor and transformer loads — it holds through the inrush without nuisance tripping, unlike a B-curve that would pop on the first start. The 6 kA interrupting capacity at 277 VAC means it safely clears a bolted fault up to that level without welding its contacts or cascading damage upstream. That's enough for most sub-distribution boards fed from a larger upstream breaker.