IBrakeForNobody: I believe they are custom pieces. I bought them from a guy on here, so I can't confirm it for sure, but I'm 99% positive they are.
jimp: They aren't sticky at all. As YUL PHL said, they are cooler in the summer and stay warm in the winter. Pretty much your ideal setup and feel better to me than leather.
Another cool thing is you can wash them without taking them off of the seats. Since they are waterproof, you can use any of the cleaners in Wet Okole's cover cleaning kit without removing the covers.