The ReBore-Zit is the only drill bit designed to enlarge a previously drilled hole while retaining the existing wire in the hole. The bit is fabricated with a hollow bodied drill bit containing a free spinning, swivel eyelet mounted to its pilot hole center shaft. Just secure your existing wire onto the eyelet and re-drill your hole to a larger size. The bit will not twist the wire. Use the appropriate ReBore-Zit bit to accommodate the preexisting hole (pilot hole) and step-up in ReBore-Zit sizes until you obtain your desired final hole size.