For temperature-sensitive specimens. Rugged, one-inch thick walls of insulation require no outer shipping box or container. Polystyrene foam mailer provides adequate space for a variety of vials, tubes or bottles. The 8 oz. Polyfoam U-Tek refrigerant pack fits perfectly into top half. Interlocking cover and body, with tape grooves, for safe mailing. Interior dimensions: 5 7/8 x 4 3/8 x 3"". Overall dimensions: 8 x 6 x 5. 1/4"".