Canon FL 300mm lens refers to two telephoto prime lenses made by Canon. The lenses have an FL type mount which fits the Canon FL line of cameras. First introduced in 1969, the FL lens replaced the R mount version, which in turn was superseded by its FD equivalent. Altogether, two variations (with two different aperture settings) were made in its short production life. The FL-F 300mm f/5.6 was the world's first lens to use synthetic fluorite crystals in its elements; those are commonly found today in its L lens.