White nylon plastic polished to reveal a smooth matte finish.
About this Product
This is a fun gadget that you can have you in house to show your friends how the sphere was printed inside the rail and you can never detach it!
http://www.shapeways.com/model/edit/605978/ [NEW] Buy the v2.0!:
http://www.shapeways.com/model/108596/rail-with-a-ball-inside-keychain.html Buy the Keychain version