In order to filter sample volumes larger than 3 liters (up to 6 liters), two Pierce Crossflow Filtration Cassettes can be connected using the Y connector accessory, which is supplied with the appropriate tubing sizes and fittings. The tubing size required for connecting the cassettes is 16, while the size needed for the pump is 15. A pump head size of 15 is required for parallel running of two cassettes.