Gemini 8000mAh 4 cell Battery
Gemini's new line of batteries are built with 4000mAh 21700 cells. A little larger and heavier that the 18650 but with higher capacity.
This 4 cell pack is 8.4V (7.4V nominal) and 8000mAh capacity. It has a built in fuel gauge on the side that displays the state of charge by pressing the button. It also has a 2-way USB-C port that can charge the pack or power your Garmin or phone.