Heavy Duty Water Cooler, also know as a chiller. This module has an integrated heat exchanger, like in a refrigator. This allows much more precise control of the spindle temperature. Als it can dissipate much more heat. Often used in in the bigger motors, in the range 5-10kw
It also has a status output, this is a potential free contact(relay). We use this in CNC systems to generate an error and stop the milling spindle, in case the chiller unit is not working for some reason.