Which of the following is NOT a requirement for DOT container properties?

The selected answer indicates that containers are not specifically required to be made of composite materials in order to meet Department of Transportation (DOT) standards. DOT specifications primarily focus on the safety, durability, and functionality of containers, allowing for a variety of materials that can achieve these criteria. While composite materials can be used, they are not mandated, hence this option is not a requirement.

On the other hand, containers must indeed be retested for use to ensure they remain safe and effective over time. This ensures that they can maintain structural integrity and safely contain materials, particularly hazardous substances. Data stamping is also a critical requirement, as it provides essential information about the container's specifications, manufacturer, and compliance with regulations. Lastly, while it might seem specific, the measurement of contents in pounds, especially for substances like propane, is vital for compliance with transportation regulations related to weight and safety limits.

By understanding these requirements, it becomes clear that the use of composite materials is a matter of choice rather than a requirement, distinguishing the correct answer from the rest.