Shotgun Jones has hit on the very reason that there is no standard choke in Sporting Clays. Those world class shots are gambling that there is more chance of missing a clay because of a hole in the pattern than because of a small pattern. Those of us not in that league are more interested in hitting most of the easy ones and not worry so much about holes in patterns! As a B class shooter(I probably should be a D). I use a 10 & 15.