This thing allows for battery changes on the Dexcom G5 transmitter.
You'll need DIY skills to cut down (or mill flat) the G5 transmitter leaving 6.5mm to 6.7mm from the flat base (6.7 gives the tightest fit).
Then remove old batteries, as per the YouTube video. (Do a search)
Clean the contacts well. I use a small rotating wire brush in a hand held hobby grinder.
I've found there's no need for solder if you spring out the bottom contacts and form the top ones into a curve so that they will be pressed down to contact by the cover.
Put in 2 new 389 batteries or the 2mm thicker SR43W batteries (recommended for longer life for higher VA & VB values)
Clip on the cover.
Engraved one colour versions of both types have been added
Test the voltage across the 2 contacts as per the Youtube video
Add a bead of silicon to make it waterproof if required, this would need cutting with a blade before the next change.
Subsequent battery changes will just be a matter of unclipping, changing the batteries and clipping the cover back in.
You will need a smartphone with Xdrip+ installed.
Dexcom readers/software don't allow battery changes
I printed it in ABS on it's side using a raft & supports with 100% infill.
You may prefer to use nylon.