3M(TM) Non-Printed Packing List Envelope NP6 is a ide load,clear polyethylene, non-printed, envelope with a strong rubber resin adhesive. Custom printing available on all standard size 3M(TM) Packing List Envelopes. 3M(TM) Non-Printed Packing List Envelope NP6 offers an easy to remove liner, exposing a high tack adhesive that holds packing slips, invoices, cards and other shipping documents securely to packages. Envelope easily loads documents from back.