Used for knot tightening.Used for PE line connection.Not hurting your fingers.The U-shaped rubber ring prevents the line from slipping.Wind and tighten the line around the circumference of the ring for at least two turns.Duralumin, which is used for aircraft as well, is machine cut and covered with the U-shaped rubber ring.Ideal for the connection of PE and leader lines by using two fingers each wearing a Shime Ring AL.Size: Outer dia.: 25.9 ? 6 mm; inner dia.: 20.2 mm; circumference: 63.8 mm; dia.: 20 1/3 mm