'Light' series: coned type (paint spray equipment and other small appliances). 'Medium' series: flat and coned types (light pneumatic tools in general engineering and allied industries). 'Heavy' series: flat and coned types (heavy type pneumatic tools such as rock drills and kindred equipment in the mining and quarrying industries and civil engineering). Working pressures not exceeding 150 lb/sq in. Workmanship, interchangeability, hydraulic testing, materials. Screw threads (B. S.P. Whitworth threads for 'light' and 'medium', Unified for 'heavy'). Illustrations, dimensions. See BS 1782.