What are two features that lockable oil sample reefers should have?

Lockable oil sample reefers are specialized containers designed to store oil samples, and their construction must include specific features to ensure the integrity and safety of the samples. Insulated walls are crucial as they help maintain a consistent temperature, preventing the degradation or alteration of the samples due to thermal fluctuations. Cold resistance is also essential because it ensures that the reefer can withstand low temperatures without compromising the quality of the oil samples inside. This helps in preserving the chemical properties of the oil, making it suitable for future analysis.

The focus of these features on temperature management is key in environments where oil samples need to remain stable and uncontaminated before testing. Proper insulation and the capacity to resist extreme temperatures are fundamental to the functionality of the oil sample reefers, making them effective for their intended purpose. Other options provided may include useful features, but they do not relate directly to the primary needs of maintaining the samples' integrity.