Holds four, Sony NP-FZ100 batteries with a snug enough fit to hold batteries securely while in a backpack. To remove a battery, just give it a little push from the hole in the 'bottom' side. I like to keep the fully charged batteries with their electrical contacts facing into the holder and drained ones with the contacts facing out. That way I can easily see, or even feel, a fresh battery when needed.

I printed mine with a 40% fill from a clear PETG and it's been in steady use for the last year plus.