Abstract: In a piston and cylinder assembly the cylinder comprises at least one annular cylinder block received in a complementary bore of a housing. A means for axially retaining the cylinder block in place relative to the housing includes a pair of slidably engaging part spherical surfaces one of which is carried by a radially displaceable member to adjust for misalignment between the cylinder block and an associated retaining component and to thereby alleviate axially offset pressure which might otherwise be applied to the cylinder block.