A fastener for a plastic bag comprising a male track including a male profile and an optional first fin extending from the male profile and a female track including a female profile and an optional second fin extending from the female profile. At least one of the first and second fins and/or one of the male and female profiles comprises a cyclic olefin copolymer or a combination of a cyclic olefin copolymer and one or more additional polymers. The cyclic olefin copolymer has a glass transition temperature, Tg, of greater than about 20° C. as determined by ASTM D3418. The cyclic olefin copolymer may comprise from about 10 to about 90 mol. % norbornene. The additional polymer is selected from a polyolefinic resin, an engineering resin, and a combination thereof.