A container spec forklift truck is one that can operate inside a standard shipping container – i.e. it can drive into the shipping container and pick up a load on a pallet that’s inside the container without the roof of the container being an issue.
The mast is usually in three segments and, fully down, will be 2200mm or less in height as a standard container is 2695mm internal height and the forklift needs to be able to lift a load off the deck to axle height. Typically they cannot lift more than five metres high due to the three mast segments being around 2 metres each and there being a requirement for some overlap between them.
However, it is possible to fit total loads of up to 45000kg in a flatrack container and forklifts designed to operate in containers usually have a rated capacity of less than 5000kg. Forklifts with a larger capacity are available (e.g. up to 10 tonnes) but, because of the low height requirements and the large counterweight needed, these forklifts are longer than usual. The longer the truck, the larger the turning circle.
A container spec forklift is not the same as a container handler which is a forklift that lifts containers and is huge.