Some great things come in small packages, this is one of them.
Imagine a chemical light that uses a battery and can easily be turned off or on when you need it.
Well that is what this is!
You can put the battery in the wrong way around and gently fit the cap so its ready to go in storage for years. Once the battery is inserted the right way around it can be screwed into place to turn on. The battery locks into place so it wont work loose. You can unscrew the cap, pull the battery and gently fit the cap on ready to go for next time.
They are bright, reliable and very effective for anything from signalling, trail marking, digging in your bergan or reading a map, taking notes, the list just goes on.
Replaceable batteries.