From their site:
How To Receive Free Shipping:
1. Add 3 or more DVDs, CDs, etc... to your Order.
2. Each Product must say Eligible for free shipping on their Item Page.
3. Order must be shipped within the United States (NO International shipments).
4. Select Ship Complete as the Backorder Method.
Restrictions:
• Eligible Products will have the 'Eligible for free shipping' link below the Stock Status on their Item Page.
• Ineligible Products will have the 'Not eligible for free shipping' link below the Stock Status on their Item Page.
• Any order containing an Ineligible Product will not ship for Free.
• Our Free Shipping offer is for Orders shipping within the United States only (NO International shipments).
• Used Products purchased from eSellers are NOT eligible for Free Shipping.
• Used products bought from DVD Empire (listed under the seller name: DVD Empire) are eligible toward our Free Shipping offer.
• Customers who wish to keep their costs low (and don't mind waiting for pre-booked or on-order items to arrive) are advised to select the 'Ship Complete' method when placing an order for maximum savings!
• If you select the 'Ship Partial' option, you will be charged the regular Standard shipping rates and per item fees for EACH Order shipped that does not meet the Free Shipping requirements.
• After your Order is completed, if you change the "Backorder Method" to 'Ship Partial' you will be charged the full Shipping costs for EACH Order shipped that does not meet the Free Shipping requirements.