Our smallest FM transmitter kit. Typical range is about 50m. Stable design, although not as stable to handling as the Mk2 kit. Has high audio sensitivity. Circuit employs two transistors. The complete transmitter PCB (miniature electret microphone included) is the size of a "AA" battery, and it is powered by a single "AA" battery. We use a two "AA" battery holder (included in kit) for the case, and a battery clip (shorted) for the switch. Estimated battery life is over 500 hours. PCB: 46 x 1 5mm.