Abstract: A valve, in particular of an extrusion blow moulding machine or a stretch blow moulding machine for manufacturing hollow bodies, has a movable piston, a process fluid region and a compensation chamber. The piston has a free front face which faces the process fluid region with a circumferential outer sealing region. At least one connecting channel connects the process fluid region to the compensation chamber. The free front face of the piston has an elevation, which is surrounded by the outer sealing region. The elevation protrudes over the outer circumferential sealing region. The valve permits a rapid and precisely timed opening.