124However, the Court of Justice has held that the Commission is not required, when assessing fines in accordance with the gravity and duration of the infringement in question, as is pointed out in the sixth paragraph of Section 1A of the 1998 Guidelines, to calculate the fines on the basis of the turnover of the undertaking concerned. It is, admittedly, permissible for the Commission to take account of the turnover of the undertaking in question, but disproportionate importance must not be attributed to that figure by comparison with other relevant factors. The Commission therefore retains a certain margin of discretion as to whether it is appropriate to weight the fines according to the size of each undertaking. Thus, in determining the amount of the fines, the Commission is not required, where fines are imposed on several undertakings involved in the same infringement, to ensure that the final amount of the fines reflects the difference in overall turnover of the undertakings concerned (Case C-407/04 PDalmine v Commission [2007] ECR I-829, paragraphs 141 to 144) or in their turnover in the relevant product market (Case T-62/02Union Pigments v Commission [2005] ECR II-5057, paragraph 159).