You can use most eBay apps for Shopify (e.g. eBay Link, Inkfrog, the Shopify eBay Integration, etc) to fulfill orders in your Shopify store via the Smart Send Premium app for Shopify.
The eBay app will sync the ebay sale into Shopify. You can then use our Premium app to fulfill the order.
To ensure weights/dimensions are correct when orders are fulfilled, please ensure the weights/dimensions of products entered in the eBay app or solution match the correct weight/dimensions of products in the My Products tab of our Premium app.