Single-sided interdepartmental envelopes are designed for confidential routing of documents between departments. Opaque material provides privacy for your contents. Fast, convenient Redi-Stik Closure is designed for repeated use. Simply press and seal. One side of the envelope is printed with a five-column format to fill in date, recipient, sender and their departments. Envelopes have an open-end closure and are made of heavy-duty 28 lb. brown kraft material.