Self Seal Poly Mailers Envelopes - White Shipping Bags (30 Bubble Mailers) Poly Mailers with an off white on the outside gray on the inside. Extremely durable and lightweight material helps save on postage. High Quality Self Sealing Mailers for shipping a wide variety of non-fragile items. Self-sealing, peel and stick, adhesive keeps contents secure and tamper proof. Strong seams, fins on two sides, and seamless bottom for maximum protection. Surface easily accepts ink, stamps, and labels Approved by shipping carriers. Best Mailers for Wet Weather Conditions.