So going out to swap 12 batteries per camera can be royal PITA to carry a lot of batteries easily. So I was dealing with couple cameras and light bulb went off. I had extra .500 S&W 50 round ammo carrier and thought diameter was close and it was perfect. I keep new batteries + end up and place dead batteries + end down. Carries them cleanly, safely, protected from weather and easy to use. Plus the ammo box was just laying around.