the engagement between the head cover 7 and the spacer 12 may be sealed the extension tubular shaft 10 is rigidly attached to the extension hole of the intermediate header guide 9 the engagement being air tight the exterior diameter of the extension tubular shaft has a sealed engagement with the internal dual piston 3 by the seal 22 the inside diameter of the extension tubular shaft 10 is larger than the exterior diameter of the tubular piston rod 4 in such a way that the space between is defining a chamber 56 the extension tubular shaft 10 has one or more orifices 57 in the close vicinity of its attachment to the intermediate header guide 9 alternatively the orifices 57 can be made in the intermediate header guide 9 the extension fixed piston 11 is rigidly attached at the opposite end of the extension tubular shaft 10 and has a sealed engagement with the piston tube 2 by seal 33 the engagement between the extension fixed piston 11 and the extension tubular shaft 10 is sealed by seal 34 the two cylinder assemblies 101 and 201 are moving relatively to each other guided by the seals 21 22 23 32 33 and the rod end cover 8 when the two cylinder assemblies 101 and 201 are put together they form pressure chambers 41 42 43 44 and 45 the pressure chamber 41 is defined in between the head cover 7 and the.