Tow hitch high quality model. It will accept perfectly different types of colors. Ready to be subdivided
Model to scale, if your software changes the size while importing, use 18 cm or 7 inches long.
Model opens without errors and doesn't require 3rd party plug-ins.
Real-world scale.
Only quads and tris, no N-Gons, as few tris as possible.
No visible UV stretching or obvious seams.
Model positioned at the origin [0,0,0].
No isolated vertices, coincident vertices, no coincident faces.
Few poles or vertices with more than 5 edges connected.