Searching for Envelopes, 13 Square (13-x-13) with Vellum (offset) appearance found in the White Color Group, 104 GSM (28/70lb Text) --learn more about White --Opaque Envelopes. Also, jump to our popular help pages for paper help. (To make a successful paper selection, it is important to have a brief understanding of text weight and cover weight papers.) AND envelope help (It is important to remember that inserts must always be smaller than the envelope dimensions.)