These are reusable igniters and they are included in devices that require them. However, sometimes they burn out, or become broken, and need to be replaced. Follow the directions that accompany your device.
A one-battery device uses 1-1/2V Glo-Plugs.
A two-battery device uses 3V Glo-Plugs.
Available in 1-1/2 VDC and 3 VDC.