The present invention therefore provides a modular system for constraining milk flow in a pressure-dependent and/or controlled manner. Due to the modular concept, the required properties of the device can be adjusted in an efficient manner. For example, it is possible to adapt the connection to a milk line, i.e., the geometry of the connection arrangement, specifically to the existing conditions of the milking stall and the milking system. The pressure-dependent constraining when milking can be adjusted specifically for a single teat or in pairs for two teats by using a respective module component. If necessary, adjustment of the range for reliable switching can be performed by selecting suitable spring components and/or by adapting the flow resistance. The flow resistance is adjustable by using a suitable connection arrangement and/or by exchanging a modular flow body.