I have a Parkzone Extra 300. The recomended battery is the PKZ1029, but of the 6 that I have. All of them have puffed up while flying the Extra, even when not usinf full throtle and flying for only 6 min. These Gforce 30C 2200MAh fit in the Extra, haven't changed shap at all after a month of flying daily. AND, you can get 3 for the price of one PKZ1029. Buy these! They work great in the Parkzone F4U too.