How to Choose Zippers for Heavy-Duty Bags?

Three months ago, I inspected a returned batch of 500 outdoor backpacks from a European distributor. The complaint was identical across every unit: zipper teeth shearing off after just 30 days of field use1. The client had specified "YKK #5 coil" in their purchase order—a reputable brand, a common size. Yet every bag failed at […]