9" x 12" First Class Envelopes get your package delivered first-class by USPS. Green diamond, first-class border grabs your recipient's attention in the mailbox. Self-sealing, Redi-Strip closure saves time and are the perfect mailroom update for concerns about surface germs. Simply peel and stick. Peelable paper strip protects the adhesive from dust to last longer in storage. Envelopes are compatible with inkjet printers but are not recommended for laser printers. 28 lb. white wove stock withstands extensive handling. Center seams add strength for heavy contents. First-class envelopes are ideal for sales literature, newsletters, contracts and more. They're a cost-effective way to send important letters and lightweight packages.