Klein Tools' 1611 Series Chicago Grips have a round inside jaw contour designed to hold weatherproof strand and solid coated wire. They also have a notched jaw to provide a firm grip on insulation. All Klein grips are manufactured from custom drop-forged steel that is machined and heat treated for excellent durability. Each grip is individually hand inspected and actuated for proper function. Grips are also rigorously tested and pulled to rated load to ensure the highest quality and reliability. Grip for Weatherproof Wire 0.53-Inch Capacity Round inside jaw contour for weatherproof coated copper wire Max Safe Load of 4500-Pound (2041 kg)