Defines pulley blocks designed for a maximum lift of 25 ton for use with wire rope with rope speed not exceeding 100 ft/min and with sheave diameter not larger than 12 in. Includes design, material, block shell, shanks of hooks and eyes, screw threads, head fittings, heat treatment, axle pins, lubrication, sheaves, locking nuts, proof load, examination after proof loading and certificate of test and examination.