20 and 40 fot containers are the 2 standard sizes i know about.
If we don't count the special containers for special purposes,
there's the 20 ft, 40ft, and also the 53 foot containers.
Ya, there's a 53 foot container that *usually* don't go on ships, but mainly used for rail and truck transport in North America.
It increases what a single truck, rail car can hold and transferring stuff between containers at ports/intermodal nodes also makes some logistical sense in some weird ways (very counter intuitive but works in the big picture) even when it seems like US is doing their own thing again.