On Geocaching.com, cache containers are classified into four sizes:
35mm film canisters and smaller containers; extremely small micro-caches are sometimes called nano caches.
Larger than a micro, but smaller than a regular; examples include sandwich-sized Tupperware and military-surplus decon containers.
Standard size ammo cans and Tupperware containers.
5-gallon buckets and larger containers; examples include large ammo cans, trunks, and jeeps.