Invisible Nylon Zippers
An invisible zipper is a zipper that is hidden within a seam. The only part that is seen is a slender zipper pull at the top. An invisible zipper is sewn in a different manner than other visible zippers.
With an invisible zipper, you do not need to bother with topstitching on the finished zipper, but rather you install the zipper before the seam it is installed in is sewn.