Lightweight, Super strong, aluminum body combined with the Dyna-Balance aluminum rotor creates a silky-smooth, retrieve with the silence and strength that are signatures of the S-concept. Spool shaft floats on the A-RB bearings for fluid handle turns and the one-way bearing doesn't allow any back play in the handle to ensure instantaneous hooksets. Cold-forged gears and Shimano's Fluiddrive ll drive train provide exceptional power. A Septon synthetic handle (varies with model) feels good on the hand which transfers into more power in the retrieve.