the potential need for rapid action in the case of unexpected market developments makes it desirable to retain a high degree of flexibility in the choice of procedures and operational features in the conduct of these operations   they can take the form of liquidityproviding or liquidityabsorbing operations   their frequency is not standardised   their maturity is not standardised  liquidityproviding finetuning reverse transactions are normally executed through quick tenders  although the possibility of using bilateral procedures is not excluded ( see chapter 5 )   liquidityabsorbing finetuning reverse transactions are executed  as a rule  through bilateral procedures ( as specified in section 52 )  ( 9 ) the maturity of the main and the longerterm refinancing operations may occasionally vary depending on  inter alia  bank holidays in member states 