Ah, I've just realized I made a mistake in a previous message. I thought 'z' was calling for the distance between the inner edge of what I'm calling 'the flange' (i.e. the edge the left-hand arrow of 'x' is pointing to), and the upright at the right end of what I'll call the 'bottom plate' (when the piece is mounted on the H960, the bottom plate is in a plane parallel to the ground - i.e. it's in a plane perpendicular to what I'm calling 'the flange'). That upright is the vertical (in this picture) axis at one end of 'z'. Having called up a flat plate, and a square, to help measure accurately, the width of the flange ('x') is 1.26 cm, and the distance from the outer edge of the flange to the vertical at one end of 'z' (i.e. the end of the 'bottom plate') is 1.57 cm at the 'bottom' of the plate (i.e. in this image), making the distance from the inner edge of the flange to the vertical edge of the bottom plate 3.1 mm - at the 'bottom' of the bottom plate. At the _top_ of the bottom plate (i.e. the inner edge, when the unit is mounted on an H960), the distance to the outer edge of the flange is 1.62cm, making the 'flange inner edge' to 'bottom plate side' distance 3.6 mm, at the 'top' of the bottom plate. So 'z', the variance between the two, is indeed 0.5 mm. Pete's spot on! Noel