Molicel P42A 21700 Battery

21700 batteries are bigger in size when compared to the commonly used 18650, but with this comes much higher options for capacity. Comparing Mah (used to measure a battery's capacity), 18650s range from 2000Mah - 3000Mah, whereas 21700 cells can get you up to 4200Mah. The end result is a vape that can run much longer, and keep down time to a minimum. 

Always check the product page to see if your device needs batteries, and if so which size is compatible.