Abstract: A stopcock with a plug which is rotary and adjustable in the housing. A fixedly mounted liner of flexible material with a smooth sliding surface is mounted in a rotary manner at a bottom part of the housing. A packing disk is clamped between inside and outside edges in the working area of a shank and projects to the outside. A gasket is located in a cylindrical annular space formed between the shank and a wall fixed to the housing. The reset force of a reset member projecting into the annular space, acts via the gasket and the packing disk on the stopcock bottom part for resetting in its conical seat in the liner. The gasket is enclosed on all sides and is supported by the packing disk by means of a pressure-proof prop ring having reset play restricted by a fixed stop on the housing. Between the gasket and the reset member, is a thrust ring tightly fitted to the wall fixed to the housing, and is centered on the stopcock shaft between the gasket and the prop ring.