The 70 mm installation depth and 76 mm overall depth leave room for wiring in a standard 100 mm deep enclosure. It mounts in any position, so no orientation restrictions in a crowded panel.
Thermal derating — the real-world current
The 20 A rating holds at 35 °C ambient. At 40 °C it derates to 18.78 A, at 50 °C to 17.48 A, and at 60 °C to 16.08 A. If your panel runs warm — say 50 °C inside — the breaker will carry 17.5 A continuous without nuisance tripping, not the full 20 A. Plan the load accordingly.