A pressure-sensitive adhesive

The coating is a pressure-sensitive adhesive (PSA, self-adhesive), of the type used for:

Self-sealing envelopes.

Self-adhesive labels.

Leaflet-labels (label booklets).

These are miniature multipage leaflets or booklets that carry information about the product. They take many forms, but usually stick directly onto the product (by PSA), thus saving further outside packaging, or stick onto the pack (sometimes inside). They are a growing sector.