Bone Tunnel Borer 2.7mm with Counter Sink. The tunnel borer has a small handle with an attached drill bit. This hand instrument is used to create a bone tunnel quickly and easily without having to set up a complete orthopaedic drill (i.e., CCL repair through tibial tuberosity). Features additional counter sink. Counter sink reduces any possible sharp edges left from drilling into tibial crest that could fray nylon line. Stainless steel. 18cm.