(20)Certain commodity derivatives, in particular based on power and gas, provide that the underlying be delivered constantly over a specified period of time such as day, month, or year. Moreover, certain contracts with longer delivery periods such as year or quarter may be automatically substituted by related contracts of shorter delivery periods such as quarter or month (so-called cascading contracts). In those cases, a spot month position limit for the contract to be substituted prior to delivery would be inappropriate, as such limit would not cover the expiry and physical delivery or cash settlement of the contract. To the extent that delivery periods of contracts for the same underlying overlap, a single position limit should apply to all the related contracts in order to properly take into account the positions across those contracts which may potentially be delivered. To facilitate that, related contracts should be measured in units of the underlying and aggregated and netted accordingly.