Simple Dynamic Microphone 2 transistor Preamplifier Kit Unassembled kit 9VDC[FK647] &lt;==Beware to Add To Cart !!! Only sold by Thaikits for product warrantee and free technical support==&gt; Require power supply 9VDC / Free 9V battery connector only sold by Thaikits It contains 2 transistor, some resistor and capacitor. ( not difficult to buid ) Comes with the schematic diagram PCB size : 1.6" x 1.3"