Abstract: The invention is a plastic cap for liquid containers, comprising a main body, which is essentially cylindrical, and an element (20) for dispensing the liquid. The upper part of said dispensing element is essentially circular, level and hinged to the main body, while its lower part is socle-shaped and is characterized by a partially cylindrical base surface (27), covered by a layer of soft material (270) sliding in the corresponding groove (30) belonging to the main body (1). Said layer of soft material (270) serves as a seal when the dispenser is open. When, on the other hand, the dispenser is closed the cylindrical projection (8) of the hole (7) of the main body, coupled with the layer of soft material (270) present on the socle, fits into the groove (30) in such a way as to ensure the seal between the dispenser and the cap body in any case.