Permanent shipping seal tape

A shipping seal tape is a permanent adhesive strip on the flap of a mailer or OPP bag. After the release liner is removed and the flap is pressed down, the bag cannot be reopened without tearing or visibly distorting it.

How it works

The strip usually carries a hot-melt adhesive that bonds aggressively to the film. In many cases the bond is stronger than the film itself, so an attempt to open the bag damages the material rather than separating the seal. This makes the closure tamper-evident: the recipient can see whether the pack was opened in transit.

Compared with a resealable strip

A resealable strip is designed to be opened and closed several times and suits retail packs where shoppers handle the product. Permanent tape is single-use and is chosen when the contents must stay closed until delivery, as with e-commerce shipments, documents and samples.

Some courier bags carry two strips, one for sending and one for returns. Match strip width and flap size to the weight of the contents.