How much capacity retain after 500 discharge cycles depends on the factors such as material of battery cell, manufacture process, circuit chipset and even the environment of using the battery would affect the result. Most manufacturers of power bank avoid to claim the percentage. It is only because the number is so awful that they feel embarrass to claim, as they use inferior materials and production technology for cost cutting. At least, Apple is dare to state that the iPhone battery is designed to retain up to 80 percent of its original capacity at 500 full charge and discharge cycles, while the MacBook Pro or MacBook Air is designed to deliver up to 1000 full charge and discharge cycles before it reaches 80 percent of its original capacity. Milkr has the same self-confidence to do so. As we share the same vision that achieving excellent user experience should be prior to cost cutting.