Battery Case for Hearing Aid Batteries (312 Brown) as a Keyring

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My friend uses hearing aids for both ears, so he always carries spare batteries with him. His battery pack is made of thin cardboard and plastic, which can fall out of his pocket when carried. The brown flip that activates the batteries should stay on until needed; otherwise, they will lose their voltage and won't work if they touch other objects in his pocket. I created a custom holder for my friend, designed to fit eight batteries snugly in his pocket. Only the middle turn, bottom, and lid are attached together, making it easy to access the batteries when needed. I made this specific design for the Type 312 Brown battery package. On the blank part of the middle section, I wrote my friend's name, but I left it out for sharing purposes. You're free to use and share this design - just remember that if you print one for someone who needs it, don't charge them for it. I assembled this holder using an M3 sink-head 10mm screw. There's room for a small spring and a 2.5mm ball, as well as detents in the lid if you want to add a snapping mechanism.