It's the line protection version — meaning it's built for feeder and main breaker duty in distribution panels, not motor protection with integrated overloads. The interrupting ratings climb to 187 kA at 240 V, drop to 121 kA at 415 V, and settle at 17 kA at 690 V, so it handles high-fault-capacity service entrances and sub-distribution boards where the available fault current is substantial. The thermal derating curve matters if the panel runs hot: it holds 40 A all the way to 50 °C ambient, then steps down to 38.4 A at 55 °C, 37.6 A at 60 °C, 36.8 A at 65 °C, and 36 A at 70 °C. If your enclosure sits near a drive cabinet or a sunny roof, size the continuous load against the 55 °C column, not the 40 °C sticker. It's a straight thermal-magnetic breaker with a shunt trip for remote opening; if you need UVR or GF protection, that's a different order code in the 3VA family.
That 76.2 mm width is a standard 3-pole MCCB footprint — it occupies three 25.4 mm (1-inch) module positions on a DIN rail or a mounting plate. The IP40 front protection means it's sealed against tools and small debris from the front, but the back and sides are open to the enclosure; keep the panel door closed and the gland plate sealed if the environment is dusty or wet.
The 3VA family is broadly stocked, but the specific variant with the shunt trip and HQ auxiliary contacts (2 aux + 1 alarm) is a configured order code — not every distributor carries it on the shelf.