What are the key features and compatibility of the Nikon Speedlite SB400 flash unit?

The Nikon Speedlite SB400 flash unit is known for its compact size, easy-to-use design, and compatibility with Nikon DSLR cameras. It offers a guide number of 21 meters at ISO 100, making it suitable for indoor and outdoor Photography. The flash unit is compatible with Nikon's i-TTL flash control system, allowing for seamless integration with Nikon cameras for automatic exposure control.