Online Help Make your personal correspondence stand out from the crowd by personalizing your letters to prospects and customers. Those businesses that use direct mail effectively, regularly use personalized letters to create a lasting impression. Personalized letters come in 3 sizes. 8 1/2 x 11, 8 1/2 x 14 and 11 x 17. Drive Thru Personalized Letters can personalize on both sides with hundreds of copy variations, fonts, and designs. Ask your Drive Thru representative for samples. Call 800-850-2248 today.