A copy of a report entitled 'Project MG/EC/80 Construction and Performance of Commercially Available Electron Microscopes a Critical Comparison produced by Dr V.E. Cosslett, Cavendish Laboratory Cambridge, for the British Iron and Steel Research Association Metallurgy (General) Division Electron Microscope & electron Diffraction Methods Sub-Committee. This contains a description of the construction and main operational features of several different types of microscopes that were commercially available in 1948. It details the practical features and makes a comment on their performance. This report was copied without permission by Metropolitan-Vickers Limited and circulated as an internal report.