6 a washer 60 and a dish shaped u cup seat 62 the return spring seat 58 has a generally circular bottom 64 surrounded by a cylindrical rim 66 and a central opening 68 surrounded by three apertures 70 the washer 60 fig7 and 8 is generally circular with larger diameter than the return spring seat 58 there is a central opening 72 in the washer surrounded by three apertures 74 the u cup seat 62 has a generally circular bottom 76 surrounded by a cylindrical rim 78 having a radially extending flange 80 there is a central opening 82 in the u cup seat 62 fig9 and 10 surrounded by three apertures 84 the return spring seat 58 the washer 60 and the u cup seat 62 can each be made inexpensively for example by stamping and they are secured together with their respective apertures aligned for example with spot welds an annular u cup 86 having a groove 87 in one face is mounted with an o ring 88 in the groove on the u cup seat weldment 56 between the washer 60 and the u cup seat 62 for sealing with the wall of the cylinder 54 an aligning socket 90 is located on the forward side of the weldment 56 and comprises a forward section with a socket 92 for receiving and engaging the rounded end 94 of the plunger 40 and a rearward section.