FLO (Flat Line Oscillation) or Spine is a process that finds where the shaft will bend most consistently and on-line to your target. Finding the spine (marked by an arrow at shaft butt), and installing the shaft in the 9 o'clock or 3 o'clock position, allows the club to perform more consistently for every swing, allowing the club to bend backward and forward on the same plane. Not finding the spine will result in an inconsistent performance, and a poorly built club, resulting in difficulty controlling your shot. This is a process we do to all our new shafts, and shaft pulls. This fee is only applied to customers bringing us a shaft from their own collection, looking to get this service done.