Bison tube

A bison tube is a small, metal, water-tight cylindrical container that can be used for micro-caches. These containers are usually small enough to fit on a keychain, and were originally designed to hold pills. The name is derived from the company which manufactures most of these types of tubes, Bison Designs.

Here's a picture of a Bison Tube

File:Bison Tube Cache Container.jpg

Sources

• Bison Designs
• Great Plains Geocache Store
• Groundspeak
• South Mountain Traders