Fujica X-mount was released in 1980 for the new Fujica SLR lineup and it replaced the M42 thread mount used on their earlier models. This system didn’t gain much popularity and was discontinued in 1985. Fuji produced lenses from 16mm to 400mm for this system and various other manufacturers also released some lenses with the Fujica X mount. 

This mount type should not be confused with the newer Fuji X -mount for digital mirrorless cameras.