[ESMA 70-872942901-36 Commodity derivatives Q&A, Q&A 2.3]

A significant number of OTC contracts are specified by reference to a quantity of the underlying commodity and not the standardised lot sizes of an exchange-traded derivative. Where an OTC contract is not defined in standardised lots the size of the contract should be calculated as a multiple of the standard unit of trading used by the trading venue for the commodity derivative to which the OTC contract is equivalent.