5:1 Design Factor. Maximum Proof Load is 2 times the Working Load Limit on 7 through 300 metric tons (except for 125 metric tons which is proof tested to 1.6 times the Working Load Limit). Maximum customer Proof Load is 1.5 times the Working Load Limit on 400 through 2000 metric tons (available on customer request at time of order 2xWLL).