That "stopper" screws in and out so you can use the "adjustable" charger. Look at the next to the last picture above.I was on so many sites, I can't remember which one had the picture of 2 flasks side by side and one had a longer nozzle. mine is the same as yours, I think I may have the stopper post (end cap) too far out (flush with the end) and when I push the flask down it hit's the chamber wall. I see yours is recessed.