Incorporating Twaron ®, the Space Age fiber pound for pound stronger than steel. Very user friendly, not stiff or twisty, won't kink or corrode or prick your fingers. The handsome black cord is pleasant to handle, easy to attach, extraordinarily strong and secure......and it does NOT stretch or slip. The regular duty cord is sized to fit the Quick Clip I. clip. Tested and proved by framers for 20 plus years.