This is the version that protects one pole (line) while switching both poles; the neutral pole is switched but not protected.
The 40 A rating at 30 °C derates to 37.6 A at 40 °C and 32.4 A at 55 °C (–). If your panel ambient sits at 45 °C, you're limited to 36.4 A continuous — a 3.6 A drop from the nameplate. The 30 mA Type A residual current trip catches pulsating DC fault currents from electronics and rectified loads, not just pure sinusoidal AC.
The 18 mm width (1 MW) means it occupies one modular unit — critical when you're packing multiple RCBOs into a sub-distribution board. Mounting position is unrestricted: horizontal, vertical, upside-down — the electromechanical mechanism and arc chamber are orientation-independent. IP20 with conductors connected, which is standard for enclosed distribution boards.