This is a brand new case of 100 #5 (12"x 15.5") unlined self-seal biodegradable poly courier mailers. Lightweight, water and tear resistant. These are great for shipping clothing, documents or other materials that don't require padding. Tamper Proof Peel and Seal Closure. 2.5 mil co-ex poly. 100% recyclable. USPS, UPS and FedEx approved.