Pre-Sized Coil Zippers, Two-Way Separating. #5 Coil. YKK brand.
Double tab sliders at each end of the zipper. These zippers can be unzipped from either end of the coil.
Two-Way Separating zippers are used on removable hammock covers (like netting or weather shield), sleeping bags, etc – Anywhere you need to be able to completely separate the two sides and reattach later (like the two sides of a jacket).
Factory sized, Two-Way Separating zippers can be shortened by cutting the top end (opened end) to the length you want.