20 Large Poly Mailers & 50 Thank You Stickers Bundle Fast and Easy adhesive strip - Easily close and ship your envelopes, no licking or water needed Pressure sensitive adhesive provides a high strength durable closure, water and dirt resistant High-efficiency mailers are perfect for shipping a wide variety of non-fragile items. Heavy-Duty Weather, Tear, and Puncture Resistant - won't bust or break open, even if over-packed.