Bible cover high quality model. It will accept perfectly different types of colors.
Model to scale, if your software changes the size while importing, use 18 cm or 7 inches tall.
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.