Our 4-Leg Bridle Wire Rope Slings are made of durable 6X19 rope & flemished eyes spliced with carbon steel sleeves. Available in 3/8'' to 1'' rope diameters. Sling Proof Testing Certificates Proof testing certificates can be supplied with your order for a nominal fee and must be requested at the time of order. Proof tests are performed in the factory where the sling is pull tested to 2x the vertical rating and officially recorded as proof for governing bodies. During the standard manufacturing process, only random slings during a production run are tested for compliance; in order to provide proof testing certificates with your order, every sling must be pull tested at the time of manufacture.