Included herein is a bat for striking a ball. The bat comprises a barrel portion, transition portion attached to the barrel portion, and a handle portion attached to the transition portion. The handle portion includes a longitudinal axis and a plurality of planes substantially parallel to the axis. The adjacent planes of the plurality of planes are positioned to define apertures substantially parallel to the axis. The planes and apertures are positioned to vary the flexibility of the handle and improve bat performance for a given swing speeds.