a flexible sachet for transporting bio - pharmaceutical liquids with a volume of 50 liters or more , of the bellows type , assumes when filled a substantially parallelepiped shape . it comprises a bottom wall , a top wall and four lateral walls . it is made of a single laminated film with three or more layers , the innermost layer being a plastics material layer that can be heat welded and is biocompatible with the media transported . a method of manufacturing the sachet is also disclosed .