Standardization: Roller containers have been standardized in DIN 30722 by the Standards Commitee on Municipal Engineering (German Normenausschuss Kommunale Technik / NKT). The first parts are subdivisions of different weight classes (part 1 up to 26 t, part 2 up to 32 t, part 3 up to 16 t) that had been first published in April 1993 and the latest revision being published in February 2007. The part 4 of the standard series covers the intermodal transport between rail and road with the issue of July 1994 being still current. The DIN roller containers have a hook that is directed 45 upwards with the handle bar positioned at a height of 1,570 mm (62 in). The roller wheels have an inner distance of 1,560 mm (61 in) and an outer distance of 2,160 mm (85 in). The width of the containers does mostly follow intermodal shipping containers and there are undercarriage frames available for twenty-foot containers to be handled as a roller container. The length of DIN roller containers is standardized in steps of 250mm from an overall length of 4,000 to 7,000 mm (13 ft 1 in to 22 ft 10 in). The height has not been standardized and roller containers are commonly not used for stacking. The NATO standard STANAG 2413 "demountable load carrying platforms (dlcp/flatracks) " references the DIN 30722 for the definition of the "hookbar". The LHS rollers and ISO container twistlock pockets are optional in STANAG 2413 - the LHS designation references the Load Handling System (German Hakenladesystem / hook load system) derived from the DIN roller containers in use for firefighting equipment