Window EnvelopesNo.: CMXEP-006Window Envelopes feature at least one opening on the front of the envelope that allows the contents inside the envelope to show through. Single Window Envelopes have just one opening for the mailing address, whereas Double Window Envelopes have an opening for the return address as well. Full Face Envelopes have an opening on the entire front of the envelope, giving a view of the contents inside. Choose from a wide array of sizes and colors to coordinate with your mailing needs, including Window Envelopes designed for standard business checks.