filter unit (22) for fitting in a filter housing (12, 14), said filter unit comprising a plurality of elements (34, 36, 38, 40) including at least one filter element (34, 36) and one hydrophobic element (38) and scrim means (42, 44) substantially enclosing said elements, opposed edge regions of said scrim means being joined together such that said elements are maintained in a predetermined juxtaposed relationship by said scrim means. The assembly of the elements into a filter unit with the elements maintained in the desired relationship by the scrim means facilitates the assembly of filter apparatus incorporating those elements.