Abstract: The invention relates to plastic bags and sack for use especially in the food and pharmaceutical industries. The bag (2) comprises inner and outer bag sections (4, 14) which are joined at least at an upper portion in a manner which allows them to be separated when required, such as by heat sealing. The outer bag section (14) may be provided with a mouth (10) through which the inner bag section can be withdrawn when required. Alternatively, the outer bag section may be peeled away from the inner bag section. The inner bag section is heat sealed after filling with contents to retain the contents in the inner portion. The heat sealing step also serves to secure the bag sections together as above. The inner bag section is preferably provided with a closeable mouth (132) separate from the end by which it is filled, through which the contents may be dispensed.