Business envelopes, also known as commercial envelopes, are characteristically open side style with diagonal seams. White #9 business envelopes measure 3-7/8" x 8-7/8" and are made from varying paper weights.

While historically the smaller sized envelopes were known as commercials and sizes 7 through 14 were called officials, the Envelope Supplies Shop uses the term business envelopes for all sizes.