A one-trip container made a single overseas voyage before being retired to storage duty — it's the closest thing to new and comes with a 30-year guarantee. Used units (graded Wind & Watertight, Cargo Worthy, or As-Is) have been in service longer; any dents, rust, or issues are disclosed up front so you know exactly what you're getting. Wind & Watertight units carry a 5-year warranty, Cargo Worthy units a 10-year warranty.