Envelope 10×4.5 size provide Elegant, bright, beautiful and affordable Envelopes. Stand out in a mailbox with unique envelope colors and styles. Shop from wide selection of business envelopes, greeting card envelopes, clasp envelopes and much more. Here we offer a wide variety of envelopes and mailing materials. Sort by color, size, and paper texture to find the best solution. An envelope is a common package item, usually made of thin, flat material. It is designed to contain a flat object, such as letter or card.