Please note: these cartridges fit only the old-style plastic tapper… will not function with the new metal tappers. By using NITROGEN BULBS, you can do two unique things: 1. You can use one Nitrogen and one CO2 bulb for your beer, which will give you a creamy “Guinness” style head when pouring a glass. 2. Use 2 Nitrogen bulbs and you can dispense wine from a Mini-Keg without adding any carbonation to your wine! Nitrogen adds a whole new dimension to our Mini-Keg system.