This is a rechargeable battery holder for when you are like me and have loads of rechargeable batteries and get tired of them falling down off the shelf all the time. It is designed for 18650, AA, and RCR123a batteries, but you could scale it for any size. I printed in ABS, which with thermal expansion makes the size a little tight on the batteries. Might increase the scale by 5% if using this or PC. Probably don't have to for PLA or PET.