What does the "O" in "CO" chain sling designation indicate?

The "O" in "CO" chain sling designation indicates "Oblong master links in each end." This designation is crucial because it informs users about the specific design of the sling. Oblong master links are used as they provide better distribution of stress within the chain, improving its performance when lifting loads. The shape of these links allows for a smoother and more stable connection within the rigging system, accommodating various lifting configurations and angles.

In contrast, other designations may refer to different features or aspects of the slings but do not specifically pertain to the master link design. For instance, the open-ended design would suggest flexibility in how the sling can be attached, while optimal weight capacity may relate to the maximum load it can carry. Overhead compatibility would denote suitability for use in overhead lifting applications. However, the specific designation "CO" is directly connected to the type of master links being used.