These Quality Park 10 x 13 interoffice envelopes have a bold personal and confidential message on all sides. Heavyweight 28 lb gray\/red paper protects your sensitive information. A heavily gummed closure keeps contents secure as your envelope travels inter office mail routes. A signature line across the flap records the sender's name. Just seal and sign to create a secure, tamper-evident package. Large boxes on back record the name of the recipient, their location and department. Inter department envelopes are a must in any office. These specialty envelopes make confidential documents obvious and recognizable to keep them on their intended course. Opaque for privacy and durable enough for any in-house mail system. 100 Per box.