A composition having at least one first component containing a perfluorinated aliphatic structure in which no more than six fluorine bearing carbons are connected in any single straight chain segment, in addition a group providing binding functionality to a surface to be treated or containing at least one polymerisable double bond or containing at least one cross-linkable group, and in addition a divalent radical containing at least one group capable of forming polar interactions or hydrogen bonds, and at least one second component containing a perfluorinated aliphatic structure in which no more than six fluorine bearing carbons are connected in any single straight chain segment and a moiety containing at least one group providing binding functionality to a surface to be treated or containing at least one polymerisable double bond or containing at least one cross-linkable group.