I just ordered a Switcheasy Tones case.
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The lighter gray parts on the back are rigid plastic. The darker color should be a firm TPU. I used the Tones on my iPhone 5 and was very happy with it. It was thin and offered very solid protection. The TPU sections never sagged or anything. A very high quality case.
Switcheasy just came out with these for the iPhone 6 so there aren't any reviews or youtube videos out yet. I'll let you know once I get it.