The Desert Fox Dimension is similar to the Head Tube Bottom Y measurement. However, while Head Tube Bottom Y is useful when using a fixture that can accurately locate the bottom edge of the head tube relative to the BB in X and Y coordinates, the Desert Fox dimension is useful for fixtures that lack a means of taking these measurements in X and Y coordinates. The Desert Fox dimension is taken from the edge of the BB shell to the point at which a horizontal line passing through the bottom edge of the head tube intersects the seat tube.