Many listings show an outside size of 8.5" x 12" and a usable (inside) size of 8.5" x 11".
Listings describe either kraft paper exteriors with bubble (polyethylene) lining or all-polyethylene (plastic) construction; both kraft with polyethylene lining and full polyethylene versions appear in the listings.
Most listings specify a self-adhesive (self-seal) closure with a tamper-evident adhesive flap.
Descriptions list bubble padding examples such as "2/16 inch" bubble lining and "3/16 inch" high-quality bubbles.
Listings offer various pack sizes, commonly 1, 5, 10, 25, and 100.
Kraft-lined mailers have smooth paper surfaces suitable for handwriting; poly mailers accept ink, stamps, and self-adhesive labels easily. One listing also notes a plain finish that provides a clear area to write addresses.