"PA66" stands for [url=http://en.wikipedia.org/wiki/Polyamide]Polyamide[/url]
"GF" stands for [url=http://en.wikipedia.org/wiki/Glass_Fiber]Glass Fiber[/url]

Saddle
PA66+GF30%
[img]http://i160.photobucket.com/albums/t188/chakkeung/20.jpg[/img]

Seat Stay
PA66+GF35%
[img]http://i160.photobucket.com/albums/t188/chakkeung/21.jpg[/img]

Part which holds the Seat (Outer Seat Tube, Seat Post and Saddle)
PA66+GF35%
[img]http://i160.photobucket.com/albums/t188/chakkeung/19.jpg[/img]

Special thanks to "得把口" for providing the nice photos. :)