Do you sell a 2 inch ball for the 600 lb dolly?
What do you mean that the shank doesnt exceed 20 mm? Most shanks for a 2 inch ball are 1 inch doameter (25 mm)
The 1/7/8 inch ball is used for a 600 pound trailer. The 2-inch ball is used for a 1500 pound trailer. No more than 20 mm refers to the diameter of the screw under the hand ball.