Adjustable for Western-style tooth patterns, the correct set is obtained simply by squeezing the handles together.
The fine-tooth model has a 1/16" wide plunger (much narrower than most) that works well on fine teeth from 12 and 26 tpi. The coarse-tooth model has a wider plunger with a greater amount of travel for use on coarser teeth (from 4 to 12 tpi).