I am not a professional piano tech, and thus can't evaluate this piece of kit on such a basis. However, I have been playing on accoustic pianos for the past twenty years, and knows how an out-of-tune piano sounds like. I bought this tool to help me get the worst strings in check when playing on unfamiliar pianos, and soon came to realize that this is my single most important tool when tuning a piano. Nothing can replace this for me now; I definitely need both the full length of the key as well as the various key heads/bits when handling different pianos. I have even read up on equal temperament tuning, and successfully tuned all 88 keys on an upright piano once (it was a full days job for me). I can recommend this tool to anyone considering tuning pianos themselves, but at the same time I feel the need to emphasize that there are reasons why piano tech is a real profession with a real education.
This hammer is very sturdy, and the parts that it is assembled from give you an impression of quality from the very first assembling. There is no moving around of parts, so as long as the piano pins fit the hole, the transition between your hand and the pin should not have any air between, giving you a better feeling.