Made from quality 24-Lb. white wove stock paper. Inside tint ensures privacy of your patient's information, and a clear film viewing window protects contents during mailing. "Return Service Requested" is imprinted on all at no additional cost. Shipped in a sturdy inner e-fluted carton that protects envelopes in transit and is great for shelf storage. FREE samples are available upon request by calling 1-800-414-0940. Overnight delivery is also available.