This high-quality, feather-resistant letter pad pays homage to the early days of airmail, when lightweight onionskin paper was used to save every gram of weight possible. The thin, translucent paper is similar to tracing paper, allowing the use of an included guide sheet to aid in writing neat, straight lines. The guide sheet is printed on one side with horizontal lines spaced approximately 9 mm apart and printed on the other side with vertical lines spaced approximately 10 mm apart.