Promar 5/16in Lead Core Rope - 600ft - The Promar 600ft Lead Core Rope 5/16in Diameter Coil is Promar's extra heavy duty rope. Perfect for Lobster hooping or crabbing in deeper water. This rope is a high tensile strength, 5/16 inch diameter leaded rope. Because it is a heavy sinking rope, this will not float on the surface. This limits the chances of the rope getting caught in the boat prop when retrieving traps.