This technical specification provides interface dimensions and cooling performance guidelines for cabinets, using water supplied heat exchangers. For a clear definition of interface dimensions and cooling performance guidelines, only cabinets have been regarded from the IEC 60297 (19 in) and IEC 60917 (25 mm) series. As the cooling performance is in direct relation to volume flows and temperatures of air and water, cooling performance guidelines are provided for two structural interface levels – Interface level 1 and 2 – of equipment built into cabinets. The third interface level is only described by main interfaces, but without detailed dimensions and without cooling performance guidelines. This interface needs very complex details for the ducting of water supply within the cabinet and down to the component heat sinks on boards within subracks. Therefore, only the principle is shown usable for individual design solutions