Comes in any length. Most kit lengths are 900mm.
Profile size is 10mm x 10mm, ±0.127mm (± .005" ).
Currently the profile is running at 9.97mm ± .01.
Attached the official STL file (link: http://www.thingiverse.com/thing:1130) and the Alibre file (link: http://www.thingiverse.com/thing:1684). Always go to the STL link for the latest version (it is uploaded directly by the Microrax inventors.
Also available on 3D content central, link: http://www.3dcontentcentral.com/Download-Model.aspx?catalogid=171&id=209894.