Existing in all forms, caches are categorized and defined in various size types. On the cache page, the cache size is listed, which is a great hint when searching for it.
One of the most common cache types, the micro is traditionally a film canister, bison tube or similar. Often they have magnets taped to them, which makes them very easy to hide in urban areas. Too small to contain regular trade items.
A normal plastic container of the smaller size, or a more sturdy and weatherproof lock n’ lock are common examples of “small” cache containers. 100ml-1l.
One liter boxes or larger, up to 20l. Is often a used ice cream containers but preferably something of higher quality. Can fit most trade items and are quite common in forests or areas away from cities, where they are more easily hidden.
Big buckets, ammocans or enormous containers. 20 liters or more. Less common considering how hard they are to hide.
Used in special cases, for example when the cache is “only” a logbook without an actual box or container.
Not actually an official cache size, but often used as a term. Nanos are extremely small containers, usually containing a very tiny logbook rolled together and no pen. Easy to hide, tricky to find. Some categorize them as “micros”, others as “other”.