ESP Stiff Rig Bristle Filament can be easily be tensioned and smoothed out to form an exceptionally straight and rigid hooklink. Terry Hearn’s mega successful Stiff Rig relies on a rigid hooklink to stand the bait off a fixed distance from the lead.ESP Stiff Rig is a low visibility clear filament with exceptional knot strength and abrasion resistance. However its key property is that once smoothed out and tensioned into a straight length it has an almost “spring loaded” quality which provides the ultimate stiff rig material.