5/16 inch coarse thread tapped forged galvanized eye nut. This product is the same forging as the EN-250, but with a different size tapped hole. [break] Working Load Limit @ 10:1 design factor is 420 lbs. The load must be applied perpendicular to the connecting surface. [break] Pro audio rigging design, roof attachment, supplemental structure, sales, support and PE stamped drawings in any US State provided by Polar Focus. Call us today for more information at (413) 586-4444.