Rough filtration is the removal of bulk solids such as grist and bulk yeasts. Process filtration often uses bags for this purpose as bags allow a high flow rate, remove a large volume of solids and are quick and easy to change out, making them economic to use. Bags are available with options of nylon mesh, polypropylene and polyester with traditional single-layer, extended life double-layer and high-efficiency multi-layer with Micro fibres incorporated for fine sediment removal. Bag filtration is commonly used to remove bulk solids, e.g. grist and bulk yeasts.