Philip Kubicki's Ex Factor bass appeared around 1983. An early Ex Factor bass was played by John Taylor of Duran Duran in the band’s appearance on Saturday Night Live. The first production model was introduced 1985. Popularity of this bass increased, with famous players including Stuart Hamm and Vail Johnson. Kubicki's  production of the Factor bass could not meet demand by this point so in 1988, a licensing agreement between Kubicki and Fender Musical Instruments was established for the manufacture and sale of the Factor bass by Fender that lasted until 1991. During this period, the main emphasis was on the development of the Key Factor 4 and 5 string basses as well as other prototypes. As soon as the Fender contract ended Kubicki was immediately back in production selling its own Factor bass line direct to the public. Until recently, Phil Kubicki was concentrating on filling special orders making custom Ex Factor basses with deluxe wood veneers.Phil Kubicki died in March 18, 2013 at his home in Laconia, New Hampshire - shortly after being diagnosed with advanced pancreatic cancer.

Source: Wikipedia - Phil Kubicki