Microfilming procedures, systems and methods differ from country to country. These differences will not affect the exchange of technical drawings and other drawings office documents if the specifications given here are followed. Microforms of technical drawings are generally produced on 35 mm unperforated film. The use of unitized microfilm carries for international exchange can circumvent the problems associated with the procedural differences in producing microforms. Specified are the reduction and enlargement ratios, sizes of enlargement and the resulting image sizes for technical drawings not larger than AO and other drawings office documents.