THe 1-4 sizes went in order from shallowest to deepest. The 'A' rim was the flattest, the 'B' the second flattest, the 'C' was the roundest, and the 'D' rim was more like a Bach rim with the higher point towards the inside. I prefer the 'C' rim out of all of them.. pretty wide and cushiony and doesn't pin the chops like the 'A' rim. The 1-4 where pretty big diameters. I prefer the 5-8 models.. 5 being the shallowest and 8 being the deepest. I love the 5C jet-tone and the 7C jet-tone is a great all around piece.. I think the diameter of those is like a .620. Lynn Nicholson played a 1A on the MF recording 'At the Top' in the 70's.. The one where he played the famous McArthur Park solo with the triple F.