With 'Banana Technology' an unconventional hybrid fabrication technology is indicated for the production of very large parabolic and hyperbolic cylindrical mirror systems. The banana technology uses elastic bending of very large and thin glass substrates and fixation onto NC milled metal moulds. This technology has matured during the last twenty years for the manufacturing of large telecentric flat-bed scanners. Two construction types, called 'internal banana' and 'external banana; are presented. Optical figure quality requirements in terms of slope and curvature deviations are discussed. Measurements of these optical specifications by means of a 'finishing rod' type of scanning deflectometer or slope tester are presented. Design constraints for bending glass and the advantages of a new process will be discussed.