Sometimes an e-mail or a text message just won't do. When what you've got to say is important enough to put pen to paper, evoke the unparalleled sentiment of the old-school mix tape by delivering your note in one of Etsy seller Enna's Cassette Tape Envelopes.

The geeky paper pockets come in sets of three envelopes for $5 and are available in red or green in Enna's Etsy shop. Bonus points if you seal them with tape from your Cassette Tape Tape Dispenser.