Zendikar Rising Set Booster Box
This is a pre-order item. Due to production issues the remaining boxes will go up for sale in what WotC is calling Wave 2.
What's a Set Booster Box? It's a different kind of booster pack, not in the structure of the original booster pack (now called a "draft" booster pack). Here's how Wizards of the Coast tells it:
Update from WotC: "Initial allocations of Zendikar Rising will be arriving in North American locations in two waves. The first wave will be at the intended launch date of September 25. The second wave will arrive in stores 7 to 10 days after the first wave’s launch. As a result, some locations may experience limited availability until the second wave arrives. Additionally, Zendikar Rising Bundles in North America and the Asia-Pacific region will be delayed and will arrive in stores as soon as possible, though they are unlikely to be available at launch."