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Bulk bags, also called flexible intermediate bulk containers (FIBCs), are versatile packaging solutions for large quantities of material. They are highly customisable with around 20 design parameters, giving you more choice and opportunity to design the perfect container to store your products.

The most basic design is a four-panel bag with a solid bottom and an open top. These FIBCs will also include lifting loops. These bags can vary in volume between half a cubic metre to two cubic metres, making them capable of carrying up to two tonnes of material. Custom Bulk Bags is a leading manufacturer and supplier of FIBCs in South Africa.

We manufacture up to 3.5 million bulk bags per year; all of which have a minimum safety factor rating of 5:1 and are produced in accordance with international regulations and quality standards. We’ve already looked at the types of bottoms available for your custom bulk bag, but the top plays just as crucial a role in the design and functionality.

White bulk bags filled with sand

Open top FIBCs

The open top is the most basic design and does not add costs to the FIBC, but it does have limited functionality. These bulk bags tend to be less common than the other designs because of their lack of protection offered. However, for companies that need an affordable bulk packaging solution for durable materials, open top bags are perfect.

These FIBCs are ideal for storing and transporting soil, rock, rubble, sand, scrap, waste materials and other products that are not sensitive to moisture or air. They are often used by construction companies and mines to move large volumes of material around the premises. For products that need to be enclosed, the next two top styles will be more suitable.

Bulk bags with inlet spout attached to filling machinery

Spout top bulk bags

These are common bulk bag styles that include a cylindrical tube sewn onto a flat top to create a fully closable top panel. The spout attaches to hoppers and filling equipment to prevent spillage or waste when filling a bulk bag. They also help to minimise dust when working with grains, sand or powdered substances.

Once the FIBC is full, the spout top can be tied and sealed completely. These bulk bags are ideal for storing and transporting sugar, grains, food, fine-grain or powdered chemicals, cement and plastic resins. The diameter of the spout can be customised to fit your specific equipment.

Duffle top FIBCs

A duffle top is a large tubular skirt that is sewn directly into the top panel of a bulk bag. This skirt can be sealed completely with strings but also opens wide enough to allow for easy filling, like an open top bag. This is the main difference between a duffle top and a spout top – the size of the opening of a duffle top allows for full open access to the bulk bags.

Duffle top FIBCs are slightly more expensive than spout tops, but they can be used in a wider variety of applications, including aggregates, animal feed, granular materials, chemicals, agricultural produce and more. This top is not recommended for dusty products and the duffle can also be customised to suit your specific needs.

These are the three most common top styles for bulk bags. Speak to one of our expert bulk bag consultants before placing an order to ensure that the correct tops are included in the design specifications. Our team will happily walk you through the ordering process and answer any questions that you may have. For more information about our bulk bags, please contact us today.


Custom Bulk Bags is a leading South African manufacturer of woven polypropylene bags for various industries, such as mining, chemicals and food. We are able to produce over 3.5-million bulk bags per year, keeping our customers in stock at all times. Our bags adhere to the highest levels of quality as a result of our stringent in-house testing and quality control programmes.

Custom Bulk Bags holds ISO 9001 certification and we currently have a number of UN-certified designs. We are a Level 2 B-BBEE manufacturer and supplier and fall under the ownership structure of Deneb Investments Limited. For more information on our products, contact Follow us on Facebook for our latest news and industry insights.

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