Features: for 4pcs 18650 Batteries holder. Special and Only for 4pcs 18650 Li-ion rechargeable battery, please install the same battery capacity/voltage-/internal resistance batteries for usage(Batteries not included) Safety with overcharge / over-discharge / over-current protections functions USB power supply max- up to 2000mA, greatly shorten charging- time- USB output 5V2A, for DC5.5x2.1mm port input and output are both 8.4V;USB port charges the mobilephones and tablets, 5.5x2.1mm port supplies power for 8.4V bicycle lights and other 8.4V devices. It has power display function and XP7 waterproof function. It is unnecessary to spot weld- the battery, which greatly reduces the internal resistance of the battery, improves the discharge performance of the battery, and effectively improves the battery life. Specifications: Item:Battery Holder for: 4pcs 18650 Li-ion Rechargeable Batteries Line length 35cm/13.78in USB power output : 5V2A max- 2000mA DC5.5x2.1mm interface- input and output : Both 8.4V Color: Blue/Red Size:approx4.7x4.5x9cm/1.85x1.77x3.54in Package Includes: 1PC Battery Power Pack Case (batteries NOT included) note: Batteries not included. Due to the problems of lighting effects and shooting angles, there will be certain tolerances in the product, please understand. Please allow 0-1cm error due to the manual measurment.