The Siemens SENTRON 5SU9406-0KK16 is an RCD-operated circuit breaker combining overcurrent and residual current protection in a single 18 mm wide module. It is a 1P+N design.
The 16 A rating at 30 °C is the base current; it derates to 15.04 A at 40 °C, 14.56 A at 45 °C, 13.92 A at 50 °C, and 12.96 A at 55 °C. If your distribution board runs warm — common in a crowded enclosure — use the derated figure for the actual ambient to avoid nuisance tripping. Supply can enter from either top or bottom, which simplifies wiring in a pre-populated board.