ISO 668

ISO 668 is the international standard that classifies series 1 freight containers and fixes their external dimensions, internal dimensions, and gross mass ratings. It defines the 20-foot and 40-foot lengths, the 8-foot width, the 8-foot-6-inch standard and 9-foot-6-inch high-cube heights, and the maximum gross mass of common types. The standard, last revised in 2020, is the dimensional backbone of intermodal interchange and the reference behind every cell guide, chassis, and stacking system.