There are many construction styles for envelopes. The three most 
common styles of office envelopes used in Federal offices are shown 
below. Critical use information are included in each procurement 
contract. Generally these envelopes are suitable for insertion of 
correspondences either manually or by automated equipment; for 
letterpress and offset printing, processing in laser printers, and 
automated mailing sorting equipment. The printed matter may include text 
and line illustrations.