When possible, Manson Reamers are made to SAAMI specs. If only CIP lists a specific caliber, reamers and headspace Gauges are made to those specs. Calibers not listed by SAAMI or CIP are made to the designer's or most common specifications. Solid pilot reamers are ground to one size which is usually slightly smaller than minimum industry bore size; they will fit most commercial barrels closely enough to produce good results. Because there is less work to make a solid pilot reamer, they're also less expensive.