It is the mounting frame that receives the removable breaker cradle — the part that stays wired in the switchgear while the breaker unit itself can be racked out for maintenance or replacement.
For a procurement or panel-builder decision, this means the chassis is sized for a 1600 A breaker frame; if the load study shows 1250 A or 1600 A, this is the correct chassis. The N breaking capacity code indicates the interrupting rating of the breaker that mounts into it — not a standalone chassis spec, but it tells you the chassis is part of a coordinated assembly with a defined fault-current withstand. Drawout mounting means the breaker unit slides into this chassis on rails and connects via disconnecting contacts — no bolted bus work to undo for removal. That makes it the right choice for main or tie positions where you want the ability to rack the breaker out for testing or swap without de-energizing the bus.
This chassis is the fixed portion of a drawout air circuit breaker assembly, installed in low-voltage switchgear lineups. It accepts the removable ENW16N breaker unit and provides the primary disconnects, control wiring terminations, and racking mechanism. The 560 mm depth, 400 mm width, and 440 mm height define the panel cutout and mounting footprint — verify these against your existing switchgear cubicle dimensions before specifying.