Both the old and the new designs have seals. I didn't know where the O-rings were in the older design (in the fittings or in the filters). Good that they are in the filters and get changed automatically. For the new style 2003 and on the seals are in the Norma quick disconnect fittings and, strangely enough, no one has addressed their replacement on any of the forums. Be sure to get my XK8 Bible at www.tothegarage.co.uk/services-1