Abstract: An apparatus and method for cooling product in a continuous hot-rolling mill. The apparatus comprises a cooling unit including a frame defining a plurality of spaced, cartridge receiving slots in which a plurality of guide and spray cartridges are removably mounted. The guide and spray cartridges are similarly configured so that either cartridge can be mounted in a given frame slot so that the number and ratio of spray to guide cartridges can be varied to modify the cooling characteristics of the cooling unit. Headers, formed integrally with the cooling frame communicate with a source of coolant under pressure and include a plurality of outlets connectable to the spray cartridges by individual conduits. Valves are provided to adjust the coolant flow rate to a cartridge and a quick release coupling is utilized to enable the cartridges to be easily removed for service and/or replacement.