I got fed up with Shaller's sloppy gearing and excessive "backlash" and changed them out for a set of the 18:1 ratio Grover's with the black shafts. While I liked the feel and construction of the Grover's, there was a small problem; they didn't stay in tune! I removed all variables and closed in on the fact that something was going on with the tuning machines, causing them to slip/not hold their tuning. I stripped down both the old Shaller's and the Grover's and found that the oblong nylon washer between the gear and the matching metal backing plate were made of different materials. The Shaller's are a clear nylon or plastic material and the Grover's are made of a much stiffer black nylon or plastic material; it could almost be mistaken for spring steel. I had always noticed that in spite of the downsides of the Shaller's gearing etc., that they would generally (after a fierce tuning session) eventually stay in tune. I installed the clear washers from the Shaller's into the Grover's and they immediately stopped slipping and stayed tuned. They can be switched out without even removing the machine heads from the mandolin, you just have to loosen the strings and remove the round gear. The black Grover washers, however, do not fit "as is" into the Schaller's; they would have to be trimmed, but you wouldn't want to use them anyways.