This brass reamer is a 1-10 taper which has been machined to +/- 0.001” The means when you ream a fitting it should be a nice snug joint connection with little effort. This universal reamer size range is just smaller than a 10mm fitting on the small end and just wider than a 19mm fitting at the widest point. Our individually sized joint forming tools have been very popular and have become trusted for their effectiveness and accuracy.