This product is component without battery core.It is used to repair and assemble batteries pack, only for people who are familiar with battery performance and have practical experience in battery assembly.,Very important thing: make that the voltage of each battery is the same before soldering the PCB.It can hold five 21700 lithium-ion batteries, but it is just a shell without the battery side.Preparation before assembly: (1). If you use new cores, please note: a. Must choose 21700 lithium battery cell, b. A group of 5 cores must be equipped with resistors and capacitors to make the voltage the same. (2). If the old battery is repaired, please test the voltage at both ends of each battery. If the voltage is different, charge each battery to the same voltage value.Colour:blackMaterial:Composite materialSize:140 x 75 x 30mmPackage Contents:1 pack x Battery HousingsOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.