def _psbl_liq_cls():
    """Returns a set of possible liquid classes available for Fluent
    """
    x = ('Water Free Multi', 'Water Free Single', 'MasterMix Free Multi',
        'MasterMix Free Single', 'Ethanol Free Multi',
        'Ethanol Free Single', 'DMSO Free Multi', 'DMSO Free Single',
        'Serum Free Multi', 'Serum Free Single', 'Water Contact Wet Multi',
        'Water Contact Wet Single', 'Water Mix')
    return x
