ISO 9175-1:1988, Tubular tips for hand-held technical pens using India ink on tracing paper -- Part 1: Definitions, dimensions, designation and marking

The purpose is that a consistent line thickness within permissible tolerances is ensured with or without lettering giudes and templates. Applies to commonly used draughting operations such as tracing, writing and lettering. Part 2 deals with performance, test parameters and test conditions.