I am not an expert on sit bone measurements and am struggling to find a saddle that does nor absolutely kill me on my new bike, but I think Specialized actually does recommend a 155 and not a 143 based on this very helpful link. The next saddle I try will be a Specialized 155, not sure which one yet, Jett, Ruby, Ariel, but my previous bike was a Specialized and the saddle is great on that one. I am oprimistic that a 155 Specialized will be a perfect fit. Here is the link http://www.specialized.com/specs/spe...eometrysaddles