Keep your flexbits centered with....BALLS?? - YouTube
Flex Bit Tips and Tricks - How to Use a Flexible Installer Bit
Klein Tools 53751 Flex Bit Auger with Screw Point, 3/4-Inch x 72-Inch Long Flexible Drill Bit / Fish Bit for Pulling Wire Behind Walls - Ship Auger Bits - Amazon.com
Klein Tools 53717 Flex Bit Auger with Screw Point, 3/8-Inch x 72-Inch Long Flexible Drill Bit / Fish Bit for Pulling Wire Behind Walls - Ship Auger Bits - Amazon.com
Klein Tools 3 Piece Flexible Drill Bit Tool Set 53721 - The Home Depot