All zippers have enameled metal double tab sliders. Marine Zipper is extremely strong and light weight with a molded zipper tooth. Chemical and erosion resistant. The polyester tape and molded Vislon teeth are designed to resist damage from ultraviolet rays. Size 10 is used for canvas, boat tops and other heavy duty applications. Questions? Send us an e-mail here on Amazon. We respond to all e-mails within 24 hours and usually much sooner. Northwest Tarp & Canvas - Bellingham, Washington