Summary I got one of the new Fatshark (Fat Shark) battery cases that use the LI-ION 18650 batteries. This is great and has a larger capacity as well as offering the ability to easily change out the batteries. The battery case is much bigger than the original and does not fit well in the strap. I designed this battery holder to allow you to easily mount the battery in your head strap without stretching it too much. The fit is actually a couple of mm smaller than the original battery. It also allows you to place the wires right next to the outlets on the goggles. I hope you enjoy these as much as I do. I printed mine with 40% infill 1.2 mm walls on all sides and in PLA.