Window Envelope with a Square Flap The #10 envelope is a versatile size most commonly used to store letterhead size paper that is folded into thirds. Just position the address to show through the envelope's window - no need to print or write the address out yourself! Moistenable Glue Seal These envelopes are designed with a traditional moistenable adhesive sealing method. Simply moisten the strip of adhesive, apply pressure, and you’ll have the perfect seal. It couldn't be easier! Easily Personalize by Using a Printer or Writing by Hand Compatible with most digital and offset printers, these envelopes are easy to customize. Want more of a DIY look? Gel Pens, Calligraphy and other hand crafts look amazing! LUXPaper is a premium stationery and office supplies brand focused on quality and variety. Our assortment of premium paper ranges from lightweight text stock to heavyweight cover stock, and every weight in between. LUXPaper products, including paper, cardstock, envelopes, and more, are available in a wide selection of sizes and in the largest variety of colors.