Ralph Glover and Ben Bauer's "needle-tilt" principle for minimizing record wear while improving sound reproduction, and Jim Kogen's engineering concept of "trackability." Shure produced the first phonograph cartridge capable of playing both long-playing and 78 rpm records, the first cartridge with tracking force of only one gram, and the first cartridge meeting the requirements of stereo recording. At the peak of Shure's phonograph cartridge production, the company was producing approximately 28,000 cartridges per day, with 25,000 of those coming from a Shure phonograph cartridge plant in Phoenix, Arizona. After the introduction of compact discs in the 1980s reduced the demand for phonograph cartridges, Shure closed the Phoenix facility but continued manufacturing phonograph cartridges in Mexico. In 2018, Shure announced that they would exit the phonograph cartridge market. Shure also developed and produced products for medical applications. In 1937, their 66A piezoelectric stethophone was designed to accurately reproduce chest sounds, and in the early 1960s, the SP-5, SP-5S and SP-6 stethoscope pickups were produced. Shure also produced hearing aid cartridges used in hearing aid products from manufacturers like Maico, Telex, Dictograph, Otarian, Vocalite, and Trimm. In 1956, Shure moved its corporate headquarters to Hartrey Avenue in Evanston, Illinois, where it remained for 47 years. Beginning in 1956, Shure manufactured magnetic tape recording heads and two years later, the company announced it was ready to mass-produce 4-ch recording heads. By 1964, however, Shure announced it would no longer produce tape recording heads due to increased competition. In 1953, Shure introduced their first wireless microphone system for performers, and in 1959, they introduced the Unidyne III Microphone, which was the predecessor to the SM57, which would be introduced, along with the SM58, six years later. Shure also produced portable equipment for broadcast field recording like Vocal Master, the M67 Portable Mixer, and the FP31 Portable Mixer. In 1990, Shure entered the wireless microphone market with the L-Series. In 1981, James Kogen, Executive Vice President, Operations, was promoted to President and General Manager of Shure. In 1995, Sidney N. Shure died at the age of 93, and Rose L. Shure was elected Chairman of the Board of Directors. In 1996, James Kogen retired; Santo (Sandy) LaMantia, Vice President of Engineering, was named President and CEO. Shure Brothers Incorporated was officially renamed Shure Incorporated in 1999. Rose Shure died in 2016 at the age of 95 In 2001, Shure acquired the Popper Stopper brand of