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M2E Pro lists Magento Grouped Product as a Single Item on the Channel by default. To list the Grouped Product as a Multi-Variational one, configure it under Amazon Integration > Configuration > Settings > Magento Inventory > Variational Product Settings.
- Product Set - a group of Products will be listed as a Set (Individual Item). Customers can purchase products only as a set. Read this article for details. Or watch this video to see how Product Sets work.
- Variations - a group of Products will be listed as a Variational Item. Customers can purchase each option of Variational Product separately.
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Find out how to calculate price and quantity for your Grouped Product in these articles: