IMPORTANT NOTE. The outer box for this tool has a notation of "4 to 12". This notation refers to the anvil graduations. It does NOT refer to the Tooth Per Inch for this tool (i.e., 4-11.). If you look closely at the anvil of the tool, you will see the stamped graduations going from 4 through 12 (max set is 4 and min set is 12). These graduations are simply to serve as a reference for the user. Both the blue colored tool and the gold colored tool have anvil graduations numbered 4 through 12. Hence, the outer boxes for both tools have the "4 to 12" notation. Apart from the color difference, the only other difference between the Blue and the Gold Saw Set is the width of the steel plunger that presses against the teeth. The 12-26 TPI Saw Set has a narrower steel plunger as this is required with the smaller saw teeth associated with a 12-26 Tooth Per Inch saw. A saw set is a tool used to bend the saw teeth in an alternating left, right, left, right fashion. The purpose of this bending is that, in use, the saw will now create a cutting kerf that is wider than the thickness of the saw blade; thereby preventing the saw from binding. This saw set has a wider plunger (compared to the blue colored model) and is best suited for saws with 4 - 11 teeth per inch (TPI). Put a ruler up to the teeth of your saw and count how many tooth tips can fit in one inch. If the count is between 4 and 11, you got the right saw set. Pressing the tool handles together causes a hardened steel plunger to protrude and push against a steel anvil. Only light pressure is needed. To use, simply place the tool over the tooth to be set, line up the plunger to bend the right tooth and push the handles together. By turning the knurled knob, the anvil is rotated (graduated from 4 to 12) thereby adjusting the extent of set achieved. Overall tool length 7". Solid die-cast aluminum construction with hardened steel anvil and plunger. Quality Made in Japan by the original patent holder for this design.