Calibration baths are used in Quality Assurance in industry and research. The modular concept is based on the combination of a calibration bath with a Unistat. This determines the temperature range and the speed of change of temperature. The calibration bath made out of stainless steel is constructed like a calorimeter and allows good homogeneity. Calibration bath with a diameter of 118 millimetres and a bath depth of 384 millimetres are offered to calibrate measurement and control sensors. The calibration space is free accessible and symmetrical. The upper edge is designed for taking a bearing with a thread for glass thermometers and, in the other side, creates a sealing ending for a customer-specific bath cover.