This is a DIY 18650 Mobile Power Bank. You can put 1 to 4 18650 batteries into the slot. Therefore， you can determine the capatcity of the mobile power bank.

Main Features:
•Simply drop in 1 - 4 x 18650 batteries to make your own power bank (batteries not included)
•Input voltage / current: DC 5V / 0.5 - 2.1A
•Output voltage / current: DC 5V / 1A， DC 5V / 2A
•Reverse polarity protection
•Flat top or button top 18650 batteries both can be used in this power bank
•With switch button
•With battery capacity indicator and output indicator
•LCD shows the capacity
•Intelligent power manage IC， overcharge protection， short circuit protection