If, in appeal proceedings, a case is remitted to the opposition division after the board has taken a decision under Article 84 EPC on the clarity of a certain feature in a claim - in the present case the weight average molecular weight of polysaccharides - this decision is res judicata and thus binding on the opposition division in the subsequently resumed opposition proceedings. The binding effect does not only cover the decision on Article 84 EPC as such; it also extends to any finding of fact that led to this decision. Therefore, if in the resumed opposition proceedings an insufficiency objection is made under Article 83 EPC on the basis that this very feature is ambiguous (insufficiency arising out of ambiguity), the opposition division should not reopen the discussion of whether this feature is clear, and should accept any finding of fact the board made in arriving at its decision on Article

84 EPC (point 1 of the Reasons).