I sell a lot of clothing on ebay and am always looking to keep shipping costs down, both for me and for the buyer. These poly mailers are perfect! They are very reasonable in price (0.12 each) and come in many sizes to fit your needs. They come with an adhesive strip to close them, and it does hold very well, but I usually run a strip of tape across just to be sure. Sharpies work very well for addressing them and I have never had any problems with durability. When mailing items first class, these do not add any noticeable weight and keep shipping costs as low as possible for my buyers, bringing in more higher bids. Larger envelopes can be sent priority mail or parcel post, once again, the envelopes add no weight to the package. If you sell clothes on ebay, these are a must have if you want to keep costs down. The other alternative is using free priority mail supplies from USPS, but that generally will cost more for the buyers. In my experience, people will bid more on items if the shipping is reasonable.