Extended versions of Hull Breach's Universal Cargo Unit (UCU) system. From Hull Breach's description:

Originally posted by Hull Breach:

The idea behind the UCU is as simple as realistic. To have a cargo unit that is alwas the same size, so you can pick up and transport it with a lot of ships and vehicles. Just like the containers on nowadays naval cargo-ships.

These extended versions include a more sophisticated built-in script to manage their artificial masses automatically, as well as changes to default block visibility in the inventory, terminal, and toolbar screens to reduce clutter. They are not fully compatible with stock UCUs, as they do not use Hull Breach's group names for control.