William Hackett Clevis Sling Hook With Safety Catch (Grade 100)These Clevis Sling Hook With Safety Catches are replacement fittings for our William Hackett Grade 100 Chain Sling assemblies. A competent person can repair and replace components on chain slings, we always recommend a proof test prior to use. (all of our sling assemblies are proof load tested prior to shipping). Size Working Load Limit (tonnes) 1 4" 1. 4 5 16" 2. 5 3 8" 4. 0 1 2" 6. 7 5 8" 10. 0