An archery toolbox for calculating proper arrow spine. In-App purchases unlock Premium Features. The app uses a configuration created from the user's bow definition and desired arrow parameters. It is the only handheld app available for shaft selection that is based on bow performance. It has the same features and flexibility as the desktop app available from Pinwheel Software. You can search by shaft manufacturer, shaft construction (aluminum, carbon, aluminum/carbon), and shaft usage (target, hunting, both). You can search the database for a specific weight range for a completed arrow (with your components), a shaft diameter range, or a specific percent FOC range. Choose to include or omit discontinued shafts. Flexible, Accurate, Unique.