The dimensions are 14cm x 9cm x 4cm. The holes are meant for 4-40 screws.
The wheels attach to a servo horn instead of directly to the servo. It is 6.5mm wide with a diameter of 70mm (roughly 2.75inches).
The stl viewer is a new find that I really like. Check out Pleasant3D
The stl and skp files are attached in the zip file.