oh I see, in that case it'd be a dealer thing, i've never seen them on a 306 myself.
part number is shown the same for both sides
servicebox peugeot is down at the moment, but looking at citroen all the BE3/4 box stuff is a round cv and anything MA is the trilobal.
looking at a C5 BE is all round again and ML is the trilobal, cross references back to xantia etc but with ME/ML boxes.
have you measured the diameter of the cv the shaft and height of the boot? that'll help massively with cross referencing.
part number is shown the same for both sides
servicebox peugeot is down at the moment, but looking at citroen all the BE3/4 box stuff is a round cv and anything MA is the trilobal.
looking at a C5 BE is all round again and ML is the trilobal, cross references back to xantia etc but with ME/ML boxes.
have you measured the diameter of the cv the shaft and height of the boot? that'll help massively with cross referencing.
need a part number? http://public.servicebox.peugeot.com/ and http://service.citroen.com/ will sort you out.