ecoEnvelope Reusable Two-Way Double Window EnvelopeSave money and reduce paper waste with innovative dual use envelope. Insert contents bottom up and seal with gummed flap. Compatible with most standard 8-1/2 x 11 invoices and statements. Recipient tears along perforation, inserts reply top down. Re-seal with second gummed seal. Remove original postage area along perforation and add new postage. Envelope Size: 3 7/8 x 8 7/8; Envelope/Mailer Type: Business/Trade; Closure: Gummed Flap.