The Siemens 3VA1120-3EE42-0AA0-ZD00 is a 3VA1 IEC frame 160 molded case circuit breaker with a breaking capacity class N rating — Icu=25kA at 415V AC. The TM220 thermal-magnetic trip unit is set for In=20A, with overload protection adjustable from Ir=14A to 20A and fixed short-circuit protection at Ii=16 x In (320A magnetic pickup). That 16x multiplier gives a high magnetic threshold — good for motor or transformer inrush where you need to ride through starting current without nuisance tripping, but it means the short-circuit protection is less sensitive than a lower Ii setting. The ATFM designation confirms it's a fixed thermal, fixed magnetic, front-mounted rotary-handle variant.
This breaker mounts in a standard IEC panel on a DIN rail or screw-fixed baseplate — the 3VA1 frame is common in distribution boards and motor control centers. The nut keeper kit (included per the order code suffix) is a detail for DC Power OEM builds in China: it retains the terminal nuts during transport and vibration, which saves a re-torque step on the line. If you're integrating into a washdown or food-grade panel, note the breaker itself is not IP-rated for hose-down; it's an open-panel device that needs an enclosure.