the tight tolerances as illustrated in fig2 and 25a the x datum corresponds to a centreline of a slot 282 in the mounting zone 210 a of the ink distribution support 210 at the fixed end of the printhead 204 and capper 208 e g at the right hand end as depicted in fig2 a which is located immediately adjacent the flexible printed circuit board 232 see also fig6 the y datum corresponds to a line 284 across the printhead cartridge 200 just above the electrical contacts 230 of the flexible printed circuit board 232 at which point the exterior surface of the printhead cartridge body 202 is at a slight angle to the vertical e g in the illustrated embodiment a clearance angle of five degrees is provided the z datum corresponds to four flat surfaces 286 on the corners of the upper portion 240 of the ink distribution support 210 which face the cradle unit 400 i e the corners of the underside of the upper portion 240 as depicted in fig2 a which is the same surface in which the slot 282 of the x datum is defined see also fig6 in this way the x y and z datums are located as close as possible to the printing zone 219 of the printhead 204 in order to reduce the effect of accumulated tolerances across multiple components providing these reference features on the printhead itself allows the printhead to be self referencing which in turn accommodates the aforementioned tight tolerances other referencing arrangements are possible so long as the small tolerances are accommodated an example of the manner in which these reference features cooperate.