A teatcup liner for a teatcup has a longitudinal shape extending along a longitudinal axis (x). The teatcup liner comprises 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 (23) and a plurality of side portions (24), each connecting two of said corner portions (23). Each corner portion (23) comprises an inner surface (25)facing the inner space (21) and having an inner radius (r) extending from the inner space (21) to the inner surface (25). The inner radius (r) is equal for each corner portion (23). Furthermore, the inner radius (r) of each of the corner portions (23) is at least 4 mm at a centre part of the corner portion (23).
