Does anyone know if I buy a set of official Merc Roof bars e.g. (S204 Roof Rails/Rack - A2048901493) will normal Thule items slot into the groove in the middle (proper fixing)
I had a official BMW set before and only BMW items would fit it e.g. BMW bike racks etc.
I've got Mercedes bars for the CLS (I think they may be made by Thule) and standard Thule items slide into the slot. I am not sure if all Merc bars are the same - I would think so - but suppliers like roofbox.co.uk sell the T slot adaptors separately if you needed to change them.