When the M-TAB pilot bit is attached to a 2" self feed bit, it becomes the full TAB installation piece. The M-TAB pilot bit is the guide to keep the 2" self feed bit on track in the proper manner. You can choose to buy the M-TAB pilot bit solo, or we have an option of buying the M-TAB bit combo. This Pilot Bit is for use with our M-TAB SL system.