Related Clues:

• Env. thickener
• Abbr. on a cover letter
• A, B or C: abbr.
• Return envelope, e.g.: Abbr.
• Some refs.
• Items included in envs.
• It's inside an env.
• 25 Across, for one: Abbr.
• SASE, e.g
• Envelope abbr
• Copier tray size: Abbr
• Check included with a ltr., e.g
• A, B, or C: abbr
• Bus. letter notation
• Personal ad abbr