The fox prop reamer was for their engines which had standard sized shafts and most engines outside of the US had metric sizes. So either by a tapered reamer or by a metric one. I my self have two reamers one standard and one metric. I find I use the standard one all the time over the metric even on the metric prop shafts. The very small amount of slop isn't noticeable in being off center. Also APC props arilled much better than they were in the past as they have jigs now.