Echo Star plastic. EVERY disc I've seen in this plastic has had more glide and therefore more D. Try it.
I just ordered 2 E* destroyers to try. I love my E* bosses, TBs and Katanas...
I agree, I like the Echo Stars. They start out quite overstable, but they don't stay that way too long. A few good hits and they are a little flippy and perfect for max D.