The S203-K20NA is a 4-pole miniature circuit breaker rated 20 A with Trip Curve K, meaning it trips magnetically between 8 and 12 times rated current — designed for loads with moderate inrush like motors, transformers, and solenoids where a standard Curve C would nuisance-trip on startup. The 4-pole configuration covers three-phase plus neutral, or you can use it as a switched neutral on a three-phase system.
Deployment context
The 4-pole format fits standard 4-module width; leave a finger's gap above and below for heat dissipation at full load.