These sturdy bags measure 3 1/8" x 2" x 5 1/8" on the outside and 2 11/16" x 1 3/4" x 3 3/4 on the inside. Available temporarily so that we can get an idea of how many seed-savers and Southern Exposure customers want this item. Metallized plastic, commonly referred to by the brand name Mylar, is a more effective moisture barrier than plain plastic. These bags also have strong seams, and are suitable for long-term seed storage. For the most reliable moisture barrier, seal them with a hot iron. Easy to label with stickers or a ball-point pen.