1. Uninterruptible Power Supply (UPS) Module, 5a High-Current Spring Thimble Version, Supports Simultaneous Charging And Discharging, Provides Stable Voltage Output, Can Measure Parameters Such As Battery Voltage, Current, Power And Remaining Power Through 12c Interface Communication, And Detects The Module In Real Time Working Status 2. Onboard Battery Protection Circuit, Preventing Overcharge, Over-Discharge, Over-Current, Short Circuit And Reverse Connection, Balanced Charging Electricity, Stable And Work 3. There Are 4 18650 Batteries On Board, Which Can Maintain Standby For A Longer Time; 4. On-Board Warning Indicator Light Makes It Easy To Check Whether The Battery Is Connected Reversely. 5. Onboard 5v Voltage Regulator Chip Can Output 5a (Max) Current, Providing Sufficient Power For Nano Output Voltage: 5V Charging Power Supply: 8.4V 2A Control Interface: 12C Product Size: About 100 x 79mm Battery Specifications: 2600mAh, 18650 Batteries X 4 (Two In Parallel And Two In Series) Through Hole Diameter: About 2.5mm Note:Different Batches May Have Differences In Product Appearance, Color, And Printed Characters, Which Will Not Affect The Use Colour: Material:Acrylic + plastic + metal Package Contents: 1 x UPS Power Module (B) 1 x Transparent Acrylic Protection Board 4 x 18650 Battery 1 x 8.4v Power Supply 1 Set x Screw Mounting Accessories Only the above package content, other products are not included. Note: Light reflection 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.