Specialty envelopes secure contents for transport, storage, and delivery. Window envelopes reveal addresses printed on envelope contents, which eliminates the need to address envelopes and contents separately. Windowless envelopes do not permit viewing of contents, which helps provide additional security. Catalog and expandable envelopes are suitable for mailing large documents that should not be folded. Coin envelopes keep track of small items such as nuts and bolts or washers and screws. Photo, CD, and DVD envelopes keep sensitive media items protected from dust and static during transport or storage.