||The F-style family of compact fluorescent lamps were first developed by Osram, and effectively the lamp is a half length version of the L-type long CFLs. Its compact form made it an alternative to the popular 2D product created a few years earlier by Thorn Lighting. Owing to Thorn's strong patents on the 2D shape it was not possible for competitors to enter that market with a lamp of the same shape.
The Osram solution does not achieve the same illuminated area as 2D, especially in higher wattage types, but is successful in presenting a similarly efficient and compact flat fluorescent lamp. In fact an advantage of the Osram design is that it provides a more uniform illuminated area, without the dark central region of 2D. However this does increase its operating temperature somewhat, with a subsequent loss of efficacy as compared to the 2D shape.
This lamp was assembled at Osram's Bari factory in Italy according to the unique glass forming method employed there, which also formed the basis of the glassworking for the subsequent Endura electrodeless lamp. Effectively the method of joining the two limbs of the discharge tube is a larger version of the cut-and-kiss technique, in which the join occupies the entire tube diameter. Two U-tubes are created and then sealed together in a planar arrangement with a small bridge join above the base. A considerable dead length of discharge tube remains in the base, this forming a cold spot and helping to maintain high lamp efficacy.
This F-shape lamp has not been a commercial success on the scale of the 2D product and today accounts for only a very small share of the compact fluorescent market.