The 125 A rating holds flat from 40 °C up to 50 °C ambient, then derates gradually to 114 A at 70 °C. That flat plateau through 50 °C is useful for panels in hot machine rooms or near furnace lines where ambient drift is common — you don't lose headroom until you cross 55 °C. Insulation voltage (Ui) is rated 690 V, and the maximum DC operational voltage is 500 V.
The 3VM frame measures 101.6 mm wide by 130 mm tall by 70 mm deep. That 70 mm depth is shallower than many equivalent 125 A MCCBs, which helps when the backpanel clearance is tight against a gland plate or rear-mounted busbars. Front IP40 protection is standard for panel-mount indoor use.