..not the 'pair' that fit above the passenger foot-well but the one under the bonnet (hood). There are TWO part number variants for this filter that I do know but here lies my confusion. Checking the MANN site I though I had sussed the correct one indeed it was confirmed by MANN as correct. So checking prices as one does I call my MB spares department and having given the chassis number I find that they are quoting the 'other' filter - which to be fair is over £7.00 cheaper. Checking the service invoices/records I had with the car from the previous owner I find that the more expensive filter had been fitted by his MB garage which ties in with the MANN filter part number ans price (give or take a couple of £'s) Now whilst I do not doubt that my local MB spares dept is wrong I do not want to fit the wrong one neither do I want to pay for a more expensive item if not needed - so can someone help throw light on the subject. My car has THERMOTRONIC 4 ZONE A/C system fitted - sales code 581, whatever that might mean?