Rotomolded ice packs are the only ones worth buying.

Yes. The ones with the hard plastic shell and welded seams. They don’t leak, they last years, and they stay cold longer than the flimsy blue gel packs from the grocery store.

The problem with most reusable ice blocks is the seal. Cheap ones are heat-sealed at the edges, and after a few freeze-thaw cycles, that seal gives out. You open your cooler to find a puddle of blue goo and soggy sandwiches. Rotomolded packs—the kind Yeti makes, or the generic equivalents—are one solid piece of plastic with the gel injected inside. No seams, no leak path.

They cost more upfront (like $15–$30 each instead of $5), but they don’t quit. Plus they’re flat and stackable, so they don’t waste space. If you’re coolering for real—camping, fishing, tailgating—spend the money. If you’re just keeping lunch cool for a few hours, thick ice cubes in a ziplock work fine, but expect a little condensation.

Don’t buy the jelly-filled pouches. They will eventually betray you.