Sperzel has been manufacturing tuning keys since 1977 with their unique design and precision machining ability which recognized in (Guitar Player Magazine October 1979) as the most significant advancement in guitar tuning capabilities.)This was the beginning of addressing the problems that have held guitar players captive for years. 1983 - Sperzel introduced the guitar world to a locking tuning key, Trim-Lok that held the string tight without tying or multiple wraps around the string post that can slip and cause staying in tune problems. Trim-Lok also has graduated post heights eliminating use of string trees, locking nuts or any other string deadening device. The Trim-Lok string locking system also makes changing strings a snap. These tuning keys are made for any guitar (elect non-tremolo, tremolo, acoustics and basses) and helps keeping them in tune longer. Another step taken for the guitar players playing enjoyment. Other major manufacturers have tried to copy this system, which proves the point that this was and still is a major flaw in the guitar industry. Sperzel has put their name on every tuning key since 1977. An American Original.