1000 10x13 Yellow Poly Mailer Envelope Bags Genuine ValueMailers TradeMarked Product Water, Tear and Puncture resistant. The inner layer provides confidentiality The self-seal closure provides a reliable, tamper-evident seal to secure all enclosures, while being opaque, the exterior film creates a crisp, professional image for your company. High-efficiency mailers are perfect for shipping a wide variety of non-fragile items.