It's a DIN-style fuse-link with blades, sold as a set of 10. The gG curve means it's a general-purpose fuse — protects against overloads and short circuits in cable and motor feeder circuits, not just semiconductor or fast-acting applications.
At 690 V AC, it's rated for the full line voltage in a 400 V three-phase system with headroom. The NH000 size is a standard DIN blade form factor — fits common NH fuse holders and switch-disconnectors in panel builds. The gG curve is the workhorse for general distribution: it handles motor inrush without tripping but clears a fault fast enough to protect downstream cables.