It's rated 125 A continuously at ambient temperatures from 40 °C through 50 °C, then derates to 114 A at 70 °C. That flat 125 A band across 40–50 °C means it holds its full rating in a warm panel without needing to oversize; the derate curve only engages above 50 °C. Breaking capacity is 53 kA at 240 V AC and 8 kA at 415 V AC — the 240 V figure covers most North American panelboard fault levels, while the 415 V number is the relevant one for 400 V-class European distribution. The 1-pole form factor (25.4 mm wide) fits standard Siemens panelboard slots; depth is 70 mm, height 130 mm.
Mounts in a standard Siemens panelboard or loadcenter on the DIN-rail or direct-mount bus. The 25.4 mm width (1 inch) occupies one pole space. No trip indicator, no voltage trigger — it's a basic thermal-magnetic trip unit. Maximum power loss is 8 W, so heat dissipation in a densely populated enclosure is manageable.