Abstract Establishes the nomenclature and lays down the leading dimensions to ensure interchangeability within the limits of system A of the following equipment: drill rods and couplings; casings, casing couplings, casing bits, casing shoes, drive shoes and casing ream shells; core barrels, core bits, core lifters and reaming shells. Specifies the characteristics of a range of equipment for drilling holes having diameters from 30 mm to 200 mm and yielding cores having diameters from 18,5 mm to 165 mm.