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.
Available sizes include:
- 2 3/8 x 5/8 in (Small)
- 2 3/4 x 5/8 in (Large)
- 2 x 3/4 in (Scuba Tank or Micro-Cache Capsule)
- 3 x 1 in (Extra Large)