Stones supposed to be flat?

Still learning my system and all the parts / pieces. Question: are the diamond stones all supposed to be flat? If I hold a couple stones ‘face-to-face’ I can see a good bit of light pass between, more so with some stones than with others.

Thanks.

I would hold a metal Straight Edge (metal ruler) onto the face of the diamond stone, see how much of a gap you see. If it is significant, snap a pic and post.