Specifies a conventional system for identifying cylinder dimensions and mounting dimensions thereof. Such a system will be composed of: a letter code for identifying mounting dimensions, envelope dimensions, cylinder fitting dimensions; a code for identifying cylinder mounting types. Although presents a code and a method of dimensioning (illustrated by 56 figures), it is not intended that all dimensions shall be standardized. Includes a listing for letter codes. This second edition cancels and replaces the first edition (1982).