9x12 Self Seal Envelopes are great for sending contracts, booklets, catalogs, magazines, important documents, everyday mail, business mail, letters, certificates, and more! These envelopes are the booklet style, meaning they are large side open envelopes. There is no folding, bending, or creasing required to fit your standard size (8 ½ x 11-inch) pages. To use, insert your items, peel the strip back, and press firmly to close. These are also great if you?re struggling to insert a slightly bulkier item. The wide side opening makes inserting a slightly bulky insert simple.