UPS Reusable Express Envelopes give you an easy way to use a single envelope for two shipments. For example, documents that need to be returned, can be shipped in a reusable envelope. Here's how it works: The receiver simply removes the old label, attaches the new label, and seals it securely with a second strip of adhesive that's built right in the envelope. Using one envelope twice cuts down on waste and is a convenient alternative for shippers, like mortgage brokers and attorneys, who ship documents for their clients to sign and return. Look for the green envelope in your company mail room.