The stainless steel cone can be mounted on all the rods that respect the chosen diameter, opens the meat of the fish and allows the fins to penetrate more easily. The hydrodynamic structure of the shaft is also benefited by the use of the cone.
Assembly: choose the cone of the right diameter, insert it on the rod a few millimeters from the edge of the fin and therefore without ever touching it, finally block it with thread locking glue or cyanacrylate.