TOUGH TYVEK PROTECTION: Made from durable DuPont Tyvek that resists tearing, punctures, and moisture, these expanding mailers safeguard important documents, books, and bulky contents through rough handling and unpredictable weather EXPANDS WITHOUT FAILING: These 10" x 13" envelopes expand up to 1.5 inches to hold binders, manuscripts, clothing, and thick stacks of paper, giving you flexible capacity without splitting seams or overstuffing damage LIGHTWEIGHT & POSTAGE SAVING: Strong yet lightweight 14 lb Tyvek mailers weigh about half as much as heavy paper envelopes CONVENIENT SELF SEAL ENVELOPES: The Redi-Strip peel-and-press closure seals instantly with no moisture or mess, plus the adhesive strip keeps envelopes ready to use even after long storage VALUE 100-PACK: Opaque white mailers protect privacy and work for shipping, mailing, or waterproof storage of tax forms, records, textbooks, and office documents, perfect for mailrooms, schools, offices, and home use