Obsidian Series 750D - Full-Tower ATX Case. The Obsidian Series 750D full tower PC case combines generous expansion flexibility, room for advanced cooling options, and an interior that's optimized for fast and easy builds and upgrades. It has a clean, elegant exterior that dispenses with arbitrary plastic add-ons in exchange for the beauty of brushed aluminum and solid steel. This rigid, rugged exterior surrounds a frame that has ample room for high-performance components and the sophisticated cooling you'll need if you're going to push those components to their limits. And, it incorporates a host of clever system builder-focused features, because building a system should be straightforward, trouble-free, and even fun.