When on a draft system Guinness has 2 lines, CO2 and nitrogen. Sometimes 1 tank with a premix. Thats what gives it a more creamy longer lasting head. The thing in the can is the nitrogen charge to replicate that draft experience. The bottled Extra Stout is just CO2. Hope this helps.
"Le Grille? What the hell is that?"
Klose 20x48 Deluxe Offset Pipe Smoker
Weber 22.5, Weber 22.5 w/Rotisserie
Weber Performer, Weber Ranch Kettle
Weber Smokey Joe, Weber Homer Simpson Smokey Joe
Bayou Classic Turkey Fryer
Brinkmann Smoke'n Grill, UDS