Abstract: A releasable check valve for use with very high system pressures. The check valve is formed such that the poppet piston is relatively smooth-running and that good action and a long service life of the seals are obtained, wherein the receiving bore has essentially the same diameter in the region of the inserts and between the inserts. A spacer bushing is arranged axially between the inserts, in which bushing the piston collar can move separating the two annular spaces on both sides of it fluidically from each other. The bore can be machined from one side, so that the inserts are centered precisely with respect to one another and the poppet piston is guided precisely. This reduces the risk of jamming and the risk of an uneven load on the seals.