Thunderbolt D/B delivers incredibly accurate performance game after game. The Dual Block weight system's unique shape more precisely counterbalances the weight extracted by drilling, producing a more consistent, stable roll, a more predictable arc, and greater hitting power. Every Thunderbolt D/B also features Ebonite's exclusive highly crosslinked polyurethane elasatomer shell, for a more controlled hook and less pin deflection. The result: better performance potential in every frame.