Igniters are used to light the firework fuse and ignite the firework reliably and safely.
Clip-on igniters are designed for clipping onto the side of a Visco fuses. They function by channeling an electric current through a tungsten coil heating element, which then burns through any fuse lacquer coating, fiber exterior and into the powder core to ignite the fuse.
One advantage of clip-on igniters is that you can clip closer to the base of the firework to cause the firework to ignite earlier.