This case replaces the stock Enacfire case so that you can put in a larger battery. It is designed to perfectly fit an 18650. The stock case has a pitiful 500mah battery that lasts about a day of listening. My new battery lasts about one to two weeks for me.
To take the stock case off, just use a thin pry tool to seperate the bottom. It was easy. The stock case has just been tacked on with some glue.
Then glue the new battery into the case somehow so it won't rattle around, and glue the case onto the earbud tray. I used hotglue because hotglue is magic.
One of the cases has small holes so you can stick your multimeter probes onto the ends of the 18650, if you are freaked out about the voltage at first like I was. The original battery has an integrated BPS(battery protection circuit) and my 18650 does not. The enacfire seems to do a great job of regulating the voltage and stops at 4.22v, so the BPS may not be necessary. By downloading this design you accept all responsibility, this design is provided without warranty of any kind.