100 9 X 12 First Class Mail Tyvek Envelopes, Self Seal 9 X 12 Catalog Mailer, Ultra Strong 14lb Tear Resistant Material for Secure Mailing, Strong Peel and Seal Flap, 100 EnvelopesFirst Class Tyvek mailers provide security for your files during transit due to sturdy DuPont Tyvek 14lb material, which is light weight, tear resistant and water resistant Our 9 X 12 inch envelopes are the perfect size for mailing standard 8. 5'' x 11'' letter paper, with a wide opening that saves times when stuffing up to 60 sheets inside Just peel and seal to create a strong permanent seal; No need to worry about your contents failing out during