Transparent sturdy plastic vials with a REE (Rare Earth Element) secured within the lid. These vials are useful for containing a log roll in a small custom-made container but are not likely to be sturdy enough to be a geocache on their own. The magnet allows for securing it in a manner that protects the cache from unexpected finds and the elements; however, they are susceptible to UV light, making them brittle over time.
They are smaller than a bison tube but larger than a nano. Inner volume is similar to a standard bison micro.