The MilliCup Flex membrane and housing are made of polypropylene which is resistant to aqueous and most organic materials. Please see the link below to review the compatibility tables for various solvents. In this table 'PP' is the abbreviation for polypropylene.
https://www.sigmaaldrich.com/US/en/technical-documents/technical-article/analytical-chemistry/filtration/chemical-compatibility-of-filter-components
See the link below to review the product datasheet:
https://www.sigmaaldrich.com/deepweb/assets/sigmaaldrich/product/documents/235/779/20352031-rev-02-19.pdf