The Bulb Holder Plastic (Red) for 8g CO2 Bulbs is the adaptor that connects an 8g CO2 bulb to the pressure valve on your home brew barrel or keg. Simply screw the CO2 bulb into the holder, pierce, and inject CO2 into your King Keg or 5 Gallon Barrel.
Use with LISS CO2 Chargers (8g). Also see the complete CO2 Injector System which includes the holder and bulbs together.