Dual cooling and calibration unit for extruding plastic hollow profiles in extrusion lines (1, 2) operated in a manner adjacent to one another in pairs, comprising at least: - one base framework (29; 29'); and - one calibration device having calibration elements and that can be mounted on the base framework (29; 29'); and - one cooling device having at least one water tank (28.2, 28.2') and one water circulating pump (27.2, 27.2') and/or one vacuum device having at least one vacuum tank (28.1, 28.1') and one vacuum pump (27.1, 27.1'); wherein the dual cooling and calibration unit is divided into two base mono-modules (21; 21') designed so as to be mirror-symmetrical with respect to one another, each of which has a base framework having an upper top-side plane (22, 22') in each case and able to be combined with one another in pairs, and the base mono-modules (21, 21') comprise a left-hand base mono-module and a right-hand base mono-module arranged in the extrusion direction; - each of the base mono-modules (21; 21') has an installation side (24, 24') as a rear side and an operating side (23, 23') as a front side, wherein the base mono-modules (21; 21') can be combined by way of their respective installation sides (24, 24') that point towards one another; - a water tank (28.2; 28.2') and/or a vacuum tank (28.1, 28.1') is arranged on the installation side (24, 24') in each base mono-module (21, 21') and a water pump (27.2, 27.2') and/or a vacuum pump (27.1, 27.1') is arranged so as to face towards the operating side (23, 23') and/or a face side in the longitudinal direction; characterized - in that the length of the dual cooling and calibration unit can be extended by in each case at least one tender mono-module (31, 31') attached to the base mono-modules (21, 21') and having an upper top-side plane (32, 32'); - in that the base mono-modules (21, 21') and the tender mono-modules (31, 31') have connecting elements (26, 26') for water and vacuum lines on their upper top-side plane (22, 22', 32, 32') in the edge region facing towards the operating side (23, 23'). - one base framework (29; 29'); and - one calibration device having calibration elements and that can be mounted on the base framework (29; 29'); and - one cooling device having at least one water tank (28.2, 28.2') and one water circulating pump (27.2, 27.2') and/or one vacuum device having at least one vacuum tank (28.1, 28.1') and one vacuum pump (27.1, 27.1'); wherein the dual cooling and calibration unit is divided into two base mono-modules (21; 21') designed so as to be mirror-symmetrical with respect to one another, each of which has a base framework having an upper top-side plane (22, 22') in each case and able to be combined with one another in pairs, and the base mono-modules (21, 21') comprise a left-hand base mono-module and a right-hand base mono-module arranged in the extrusion direction; - each of the base mono-modules (21; 21') has an installation side (24, 24') as a rear side and an operating side (23, 23') as a front side, wherein the base mono-modules (21; 21') can be combined by way of their respective installation sides (24, 24') that point towards one another; - a water tank (28.2; 28.2') and/or a vacuum tank (28.1, 28.1') is arranged on the installation side (24, 24') in each base mono-module (21, 21') and a water pump (27.2, 27.2') and/or a vacuum pump (27.1, 27.1') is arranged so as to face towards the operating side (23, 23') and/or a face side in the longitudinal direction; characterized - in that the length of the dual cooling and calibration unit can be extended by in each case at least one tender mono-module (31, 31') attached to the base mono-modules (21, 21') and having an upper top-side plane (32, 32'); - in that the base mono-modules (21, 21') and the tender mono-modules (31, 31') have connecting elements (26, 26') for water and vacuum lines on their upper top-side plane (22, 22', 32, 32') in the edge region facing towards the operating side (23, 23').