A droplet deposition head including a datum surface arrangement for alignment of the head relative to an external mounting component in either a vertical mounting mode in which the head is held against a vertical mounting plate or a horizontal mounting mode where the head is held against a horizontal mounting plate. The datum surface arrangement comprising at least seven datum surfaces (x1; y1, y2, y3; z1, z2, z3) provided on the head, wherein five of the seven datum surfaces are provided for alignment in both vertical and horizontal mounting modes, and wherein a sixth datum surface (z3) is provided for alignment exclusively in said horizontal mounting mode and a seventh datum surface (y3) is provided for alignment exclusively in said vertical mounting mode.