Amazon size requirements in the United States:

Boxes containing multiple standard-sized items must not exceed 25" (64cm) on any side.

The process for sending oversized items to FBA is no different from that for ordinary items, but the storage fees for oversized items are higher than those for standard-sized items, so the loss from unsalable oversized items will be greater!

Amazon US FBA also has its specific regulations for overweight items, "Amazon FBA Notes".

US FBA overweight regulations:

1. The box must not exceed the standard weight limit of 50 pounds (22.7kg), unless it contains a large item weighing more than 50 pounds

2. For large items weighing more than 50 pounds, a label clearly marked "Team Lift" must be affixed to the top and side of the box

3. For large items weighing more than 100 pounds, a label clearly marked "Team Lift" must be affixed to the top and side of the box

4. For large items weighing more than 100 pounds, a label clearly marked "Team Lift" must be affixed to the top and side of the box

5. For large items weighing more than 100 pounds, a label clearly marked "Team Lift" must be affixed to the top and side of the box

6. For large items weighing more than 100 pounds, a label clearly marked "Team Lift" must be affixed to the top and side of the box

7. For large items weighing more than 100 pounds, a label clearly marked "Team Lift" must be affixed to the top and side of the box

8. For large items weighing more than 100 pounds, a label clearly marked "Team Lift" must be affixed to the top and side of the box

9. Large items weighing more than 40 pounds must be labeled "Mechanical Lift" on the top and sides of the box.

4. Boxes containing jewelry or watches must not exceed 40 pounds