The Schneider A9L16669 is an Acti9 iPRD40 Type 2 surge arrester — 4-pole, MOV-based, rated 230/400 V AC. The 40 kA max discharge (common mode L/PE and N/PE) and 15 kA nominal handle the kind of transient energy you see on a TN-C earthed supply in an industrial or commercial building.
Type 2 SPD per EN 61643-11 and IEC 61643-11 — that's the class for sub-distribution boards, not main incomers (Type 1) or device-level (Type 3). The 15 kA nominal discharge (In) is the test current it survives repeatedly; the 40 kA max (Imax) is the one-shot survival limit. Protection level <1.4 kV (Up) means it clamps the surge low enough to keep downstream equipment safe, assuming the associated breaker — iC60N/H/L at 40 A curve C — is paired correctly. The tunnel terminals accept 2.5 to 35 mm², so it takes the incoming supply cable directly.
Clip-on DIN rail, 8 pitches of 9 mm wide — that's 72 mm total width. Height 81 mm, depth 69 mm. The white (RAL 9003) housing blends into a standard panel. IK03 impact rating means it handles light knocks during installation.