Cargo holds are installable equimpent that increase the maximum capacity of a ship's hold. Only one cargo hold can be installed on a ship at a time.
The maximum expanded size of a ship's cargo hold limitied by the ship's specification. The Wolfen and Sapphire can both be increased by the size of the largest standard cargo hold, wheras the EI500 can never be expanded and will only benefit from a cargo hold's extra properties.
Custom ships with cargo expansion limits larger than one hundred tons require custom cargo expansion itemes to make full use of their potential.