The Ko-ken RS4127/6 1/2" Square Drive Nut Twister Set is designed for efficient removal of rounded-off bolts and nuts, featuring a unique helical structure with six teeth that taper inward for a secure grip. This versatile set includes sizes 17mm, 19mm, 21mm, 22mm, 24mm, and 25.4mm, making it ideal for use with various round bolts, including stud bolts and cap bolts, provided the correct size is selected and the fastener is intact. Each socket measures 42mm in length and is securely mounted on a 200mm rail for easy organization and accessibility.