From small furniture exporters to heavy machinery shippers, picking the right container type and size is one of the most important decisions you make before booking space. This guide explains what a modern ISO shipping container is, compares standard 20ft, 40ft, 40ft and 45ft high cube, and 40ft open‑top containers by internal dimensions, door openings, volume, and payload, breaks down when to use dry, high cube, open top, flat rack, reefer, and tank units, shows how region‑specific port, road, and rail limits affect your choices, and shares real case studies of furniture, machinery, and electronics shippers who cut per‑unit freight costs by 30–40% simply by switching container types and optimizing how they pack each box.