The class Fixed_alpha_shape_cell_base_3<Traits,Fb> is the default model for the concept FixedAlphaShapeCell_3.
The class has two parameters. The traits class Traits provides the number type for alpha values. The second parameter Fb is a base class instantiated by default with CGAL::Triangulation_cell_base_3<Traits>.
#include <CGAL/Fixed_alpha_shape_cell_base_3.h>
Fb