the rear of the collar 62 is a circumferential groove 64 which receives a rearward annular flange 65 the rearward annular flange comprises two identical semi annular members each of which has a first radially extending web 66 and a second longitudinally extending web 67 and the two semi annular members are assembled upon the collar 62 in the groove 64 by means of a split ring 68 which surrounds the longitudinally extending web 67 and snaps into aligned circumferential grooves 69 in said web 67 the universal mounting 55 is protected against dust and dirt by a first flexible annular boot 70 and a second flexible annular boot 71 which are mounted respectively at the front and at the rear of the ball and socket means 55 the boot 70 has a longitudinal portion 72 which closely embraces the cylinder 45 and is held in place by a split retaining ring 73 and the boot has a rearward internal flange 74 which snaps around a forwardly extending annular rib 75 that is formed integrally with the forward socket element 57a the second boot has a longitudinal portion 76 which closely embraces the head end 46 of the cylinder 45 and a split ring 77 snaps around the longitudinal.