These lab created rubies are made with flaws in them to look more like natural rubies. They match the chemical properties of a natural ruby and have a hardness of 9 Mohs, they are cut like natural rubies in a way to avoid surface flaws, so each gem is cut slightly different.  Bad looking stones are discarded, so all look good and are highly polished.  The colour and slight opacity of the stone combined with the high polish make this a very good looking stone, the bigger stones look better.