A top stop made of a flexible material that cooperates with at least a portion of a slider body. The top stop includes a body having a fin that extends upwardly from the body and that includes a contour that generally conforms to a leading edge of the slider body. In some versions, the top stop has a gap that is configured to snuggly receive a connecting neck of the slider body in such a way that water is prevented from penetrating the slider body. In some embodiments, the top stop includes two extensions, at least one of which has one or more sliding surfaces that are configured so that the slider assembly produces an audible noise when the connecting neck is snuggly received within the gap and the assembly is in the locked position.