Abstract: An instrumented baseball or softball bat knob comprising a knob housing including a generally cylindrical member inserted into a handle end of the bat and a knob portion attached to the cylindrical member. The knob portion has a diameter that is larger than a diameter of the handle end of the bat. An electronics package is mounted within the knob housing and includes one or more sensors, a microcontroller (processor), memory device and a battery to generate and store data relative to conditions of a batter's swing. The electronics package may also include a wireless transmitter/antenna/transceiver to transmit swing condition data to an external, remote processing unit.