It's the thing you put ahead of a contactor to keep a pump or conveyor motor from cooking itself on an overload or taking out the whole panel on a short. In a plant with big transformers feeding a 400 V bus, that 100 kA rating means you don't need a current-limiting fuse upstream to protect this breaker.
That's the same rail every panel builder uses — no special adapters. Width is 45 mm, depth is 97 mm. Mounting position is any — you can lay it sideways or upside down inside a tight cabinet and it'll still trip correctly. The clearance around it: 50 mm above and below, 30 mm to the side, nothing needed front or back. The screws take a Pozidriv size 2 tip, or a 5-6 mm diameter screwdriver shaft — common tools on any electrician's belt.
Environmental and operating limits
That -20 °C floor matters if this breaker lives in an unheated pump house in a northern winter — it'll still trip on overload at freezing temps. Rated voltage range is 20 to 690 V.