These products are mainly produced under very rigorous growth controlled conditions using chemical vapour deposition (CVD) techniques and are later subject to high quality control procedures. The resulting single crystal synthetic diamond is an engineered material that is highly consistent in its properties and behavior.
NEVERTHELESS, using single-crystal diamond instead of polycrystalline diamond in such applications has advantages. Because the C—C bonds that hold its patchwork of tiny crystals together are weaker than C—C bonds in single-crystal diamond, polycrystalline diamond isn't quite as thermally conductive, as optically transparent, or as strong as single-crystal diamond.
In fact, for some applications--particularly those such as electronics that require the highest carrier mobility--only single-crystal diamond will do.