The 52 A continuous rating at 480 V and 600 V matches it to a 40 hp motor at 460/480 V — so if you're feeding a 40 hp pump or conveyor drive, this breaker is sized for that load.
The 55 mm width is a single modular unit, so it occupies one slot on the rail. Clearance requirements: 50 mm above and below, 10 mm to the side, zero forward or backward. That 50 mm vertical gap is the one that catches people — if you're packing breakers in a row, leave that headroom for arc-chamber venting. Terminal capacity for the main contacts: 2x (1–35 mm²) or 1x (1–50 mm²) solid or stranded, with M6 screw terminals. That's enough for the 52 A feed conductors.