The groove is very wide and deep. I haven't seen such a deep groove H.G.Co. in ages.. Is there anything different here? It is almost like a CD 165 bottom with a CD 164 top.. The groove is so large..It was very odd when I first saw it and maybe I just haven't handled a common piece of glass in a while and I'm getting a little older and forgetting my glass...HELP!.......... thank you