This product is componentwithout 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. before assembly: (1). If a new core is used, please note: a. 18650 power lithium battery core must be , b. A group of 5/10 cores must be equipped with resistance and capacitance to make their voltage the same. (2). If the old battery is repaired, please test the voltage at both ends of each cell. If the voltage is different, please charge each cell to the same voltage value. Very important: that the voltage of each cell is the same before welding PCB. This is the Plastic Case, it can fill 10 pieces of 18650 li-ion power batteries, But no battery cell in it !!!!!! Colour: Black material: plastic Package Contents:1 x battery Plastic Case set Only 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.