Cartisan Pro Pen NEO 400 510 Battery

The Pro Pen NEO 400 is the smaller of Cartisan's two NEO batteries and differs from the NEO 900 mainly in cell size — the number in the name denotes capacity in milliamp hours across this line. Both share the colour digital screen that shows and changes the voltage step, and both use 510 threading. It comes in five colours, including a rainbow finish. If you rarely get a chance to recharge while out, the larger sibling is the better pick; the 400 is the slimmer option for a trouser pocket.