Tension Envelope Corporation is one of the leading manufacturers of envelopes in the United States. The company sells its products directly to companies and organizations. The company specializes in making the types of envelopes customers get in the mail and use on a daily basis, such as its featured line of photo packaging envelopes. Tension Envelope Corporation s products range from standard sizes and styles of mailing envelopes to unique specialty envelope products. It manufactures more than 12 billion envelopes a year from plants spread throughout both coastlines of the U.S. The company also maintains more than 30 sales and service offices in major U.S. markets, including its location in Fort Worth, Texas.