A handwritten note lends significance to any personal or professional correspondence. If you are on a first-name basis with your customers, you should consider Monarch size letterhead rather than the standard 8.5" x 11" sheets.
Monarch Letterhead (7.25" x 10.5"), also referred to as Executive letterhead, is usually folded in thirds to fit in Monarch size envelopes (3.875" x 7.5"). Monarch letterhead is designed for social letters, (often handwritten) or informal business communication.
Use Monarch letterhead in businesses where a personal touch might be helpful.