High Density Weekly Pre-Portion Bags are made of our high density polyethylene (HDPE) which is a very durable and flexible material. Operators pre-portion their food and use the food rotation system to: Save Money: ensure the exact portion and subsequently the same food cost every time. Save Time: operators will sell plates faster during busy times and turn tables quicker. Build ConsistentPortions: customers want the same portion every time. Practice Food Safety: improperly stored food is one of the leading causes of a food-borne illness.