These shorter, four inch tips are part of the "Spin" interchangeable set by ChiaoGoo. The smooth bamboo needles have the darker, patina finish and are warm in your hand. These are not complete needles, you need to attach them to cords to create circular needles. They work equally well with the red "Twist" cords as the nylon "Spin" cords. They will only interchange and attach to cords made by ChiaoGoo. Be sure to purchase the correct size cord for the size needle. US 2 (2.75mm) through US 8 (5mm) take small cords, while US 9 (5.5mm) through 15 (10mm) take large cords. The four inch length has the special ability to be used to make sixteen inch circular needles when paired with eight inch cables.