This is a mount for battery packs, specifically tailored to fit on the Devaso headband for the Meta Quest 3. It is fixed centered, ideally with strong glue or double sided tape. 

The dimensions of the battery pack holder are tailored to the “VRURC” external battery with 10.000 mAh capacity and similarly sized ones. Via the .step or .skp file it should be possible to easily adjust it for the length and width of other battery packs. 

The height of the battery pack doesnt really matter as a velcro tape (up to 2 cm in width) is utilized to secure it. Just use one of appropriate length to fasten your own battery pack. 

Even with the adapter attached the Quest 3 should still fit into most cases that would also offer room for the official Elite strap.