ITEM NAME:3S 18650 Lithium Polymer Li-ion Battery BMS Protection Board With Balanc 1x Hote Descriptio n Description: Features: 1. The user can freely set 3 strings of 4 strings or 5 strings. The default.The user can freely set 3 strings of 4 strings or 5 strings. If you need other strings, you can choose when ordering. The better the battery consistency, the longer the battery life and the best performance of the protection board.