"Relative to the bore diameter" is a concept that many who turn steps on brass bars simply can't comprehend. Many are learning indirectly without vast practice in mensuration because those lovely sets of choke tubes don't have the interchangability between guns and gun brands that they expect they should. Skeets is affordable; it works. Baker has the price; Galazan the price and the cachet. Pay what you wish but get something that "measures something" as Eightbore says.

jack