The basics YKK Unique Invisible Zippers are wonderful for all your projects that you don't want the zipper to be seen. The benefits 100% Poly Tape.  9", 14" and 22" lengths available. The uses Works well for formal wear, velvets, dresses, pants, crafting projects and home decor. The bottom line Coil interlocking, nylon teeth (teeth size = 3mm). Closed.