In a tap cock (10), the opening (28) of the cock plug (18) is formed by a lateral recess in the cock plug (18) on one side of the axis (26) of rotation of the said plug. The axis (24) of rotation of the plug (18) is offset sideways relative to the common axis (56) of the inlet passage (20) at the outlet passage (22). The cock plug (18) is composed of ceramic material. <IMAGE>
