The #10 Envelopes Letter Size Self Seal by Splendoress are rectangular in shape and made of white woven paper with a 24 paper weight. These self-seal envelopes are windowless and feature a #10 security design, making them ideal for secure business transactions. With a size of 4.125-x-9.5-inch inches and a 500 count quantity, these envelopes are perfect for sending letters and documents with confidence. The manufacturer part number is #10 Security Envelopes Windowless, and the product dimensions are 11.5 x 10 x 4.25 inches. This product is not discontinued and weighs 6.06 pounds.