What feature is notable about IBCs in terms of structure?

Intermediate Bulk Containers (IBCs) are designed to be versatile in their structural qualities, which is a key aspect that makes them suitable for storing and transporting a wide range of hazardous materials. The notable feature of IBCs is that they can be both flexible and rigid, depending on their design and the materials used to construct them. This flexibility allows them to adapt to different types of contents, making them effective for various applications in industries handling hazardous materials.

The ability to be flexible helps in reducing the overall weight when empty, facilitating easier transportation and handling, whereas a rigid design may be preferred for certain applications where durability and shape retention are critical for the storage of hazardous substances. This adaptability is vital for safety and efficiency in handling materials that can vary widely in consistency and chemical properties.

In contrast, the other options do not accurately represent the characteristics of IBCs. They are not exclusively heavy, nor are they only collapsible or restricted to a single size, as IBCs come in various dimensions to meet different storage needs. The flexibility in their structure allows for a broad range of applications, highlighting the importance of this feature.