Lisa, you raised a great question. Just measured my sit bones with white paper, and they come out to 5' and 3/4 inches. I guess B17 would be too narrow for me so best bet would be to go with Brooks B17 regular and I can always either return or sell. The rails are 8cm long on Brooks b17 which is a big difference I guess, but since it's better for me width wize.... Thanks for all your help, will order Brooks today and see how it will like my butt.