Extra sturdy metal zips. 1.25 inches wide. These guys are pretty tough. Put them to work! These beautiful zippers are deadstock YKK zippers from a small apparel brand that is closing shop. We acquired these along with two palettes of fabric and lots of other fun notions like wood and fabric-covered buttons.
Shipping charges are minimal once you buy your first item, so it's just good budgeting to buy at least two items while you're here. Zips in particular are much more worthwhile when purchased in multiples.