The standard tolerance of all dimensions on our crystals is +/- 0.1 mm. The two potential exceptions to this are the outer diameter and the total thickness of the crystal and reasons may vary from lack of availability of a suitable diameter source rod of sufficient quality (e.g. cutting a 8x8 mm square shape from a 10 mm diameter rod leads to rounded corners) and details of the polishing process (tighter alignment tolerances mean we have to make more corrections to the orientation of the surface normal in later stages of the polishing process which can compromise the total thickness of the crystal at the expense of an accurate alignment).