I think that for conventional lines (that is other than tippet or leader material) that fishermen and manufacturers use the line's nominal breaking strength as a measure of relative diameter. That's why the power braids give an approximate breaking strength like 20lbs. but a diameter comparing it to a mono line's breaking strength of around 6lbs. I think that fishing line ads are kind of strange because they talk about making the world's strongest line as if one type of 6 lbs. line breaks at higher than 6 lbs., what the heck does that mean? Is it then really an 8 lbs. line? One thing I noticed is that for leaders and tippets that Maxima diameters are large for their stated breaking strength. I think their 3x is rated for 5 lbs. breaking strength where most 3x tippets are rated between 8 and 11 lbs.