   When a sling is used in a basket configuration, an adjustment to the load rating of the sling must be made based on the size of the object to be lifted. The rating of the sling must be reduced depending upon the raito of the size of the object being lifted (D) and the diameter of the sling (d). The method used to determine the loss of strength or efficiency is referred to as teh D/d ratio. For example, when a 1 inch wire rope sling is used to lift an object that is 10 inches in diameter, the D/d ratio is 10 to 1 or 10/1. This adjustment applies to wire rope and chain slings but not to synthetic slings. 
The D/d ratio can also apply to the hook that is lifting the sling.
This is shown in the figure below.
For wire rope, the capacity reduction in percent of rated capacity is given in the table below. 
For chain, the capacity reduction in percent of rated capacty is given in the table below. 
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