It depends on your project! Nylon Coil works the best for curved seams, tolerating horizontal stress, and as a general-use zipper. For straight seams, heavy materials, and an upscale look, a Metal Zipper is a good fit. Molded Plastic zippers are commonly used in outdoor, kid's, and casual clothing. Or use an Invisible Zipper anytime you'd prefer a hidden zipper, like in formal wear.