You’ve probably seen this happen. Two bags sit side by side on a shelf, look identical, and get loaded with the same product. One tears within a week. The other is still fine a year later. It feels random, but it usually isn’t.

Thickness is the first factor, and it’s measured in microns or mils. Thicker usually means stronger, but consistency matters just as much. Film that’s heavy in one spot and thin in another will fail at the thin spot every time, no matter what the label says.

Then there’s the resin. Different grades of polyethylene stretch, tear and resist punctures in different ways. A decent manufacturer picks the grade for the job, instead of whatever happened to be cheapest that week.

Seams matter more than people expect. Most bag failures start at the seal, not in the middle of the film. A wide, clean seal can handle a lot, while a narrow or uneven one gives up early.

Storage plays a part too. Sun and heat age plastic over time, so bags should live somewhere cool and dry. Even a great bag gets brittle after a summer next to a hot window.

When you’re shopping, compare actual polyethylene bags and liners by testing samples with your own product, not by trusting a catalog. Fill one, drop one, stack one, and see what happens. Ten minutes of rough treatment tells you a lot.

If what you’re packing is heavy or abrasive, like salt, talk to a polyethylene salt bags manufacturer who handles those loads daily. They tend to have strong opinions about gussets, seals and film blends, and those opinions usually come from fixing real problems.

A bag is a tiny slice of your total cost, yet it carries everything you sell. Choosing it carefully is one of the cheapest ways to protect your name.