Worm-proof and Zerust

Soft plastic baits are made from PVC plastisol loaded with oils, and those oils attack ordinary polystyrene. Leave worms loose in a cheap tray for a summer and they will fuse to the bottom and warp it. Worm-proof trays use a plastic that resists this.

Zerust is a separate technology that addresses steel. The tray plastic or an included strip slowly releases a vapor corrosion inhibitor that coats metal surfaces inside the closed box, which keeps hooks and split rings from rusting between trips.

Neither matters much if you fish once a month in a dry climate. Both matter a lot if your tackle lives in a humid garage or a boat.

The inhibitor is not permanent. Zerust strips are usually rated for about a year and the vapor released by treated plastic fades over time, so a decade-old tray is not still protecting anything. Replacing a strip costs a couple of dollars.