Doh! I completely misread that question! I prefer NATO cans. The cap on them seals much better. US Spec cans have a different mouth that can be more troublesome. YOu need to make sure ou have good gaskets and a way to close/open them (a Leatherman Wave works well as a tool). They use different spouts. NATO cans are easier to pour cleanly straight from the can into a funnel. Capacity is about the same. US Spec is 5 gallons while NATO is 20 liters (5.2 gallons).