Custom as usual
These tubes are designed to hold 1x18650 battery or 2x123 size batteries.
I had the caps done in high-vis orange so your spares are easy to see in the bottom of a bag or pack. They are square to provide anti-roll capability.
Fresh batteries get stored with the + terminal towards the "head" of the battery tube. (think of it like a mini flashlight) When you deplete a battery, store it with the + terminal towards the tail.
Since the tubes are clear, you can tell at a glance whether the battery is fresh...or dead. Cool huh? Around here we call that product design.