A teatcup liner for a teatcup has a longitudinal shape extending along a longitudinal axis (x). The teatcup liner includes a barrel (2) having a length (L) and defining an inner space (21) for receiving the teat. The barrel has a polygonal cross-sectional shape transversely to the longitudinal axis along the barrel. The polygonal cross-sectional shape defines a plurality of corner portions and a plurality of side portions, each connecting two of the corner portions. Each corner portion includes an inner surface facing the inner space and having an inner radius extending from the inner space to the inner surface. The inner radius is equal for each corner portion. Furthermore, the inner radius of each of the corner portions is at least 4 mm at a centre part of the corner portion.
