Check the listing for details. THT Electronics Soldering Practice Circuit Board Kit - Flip Flop Circuit. Condition: New. Listed at 7.99 USD. Through Hole Soldering Practice Kit - Flip Flop Circuit This is a kit I designed for those who are learning to solder or just need a little practice before jumping into a repair/build. Included are 26 resistors, 2 capacitors, 2 transistors, 2 LEDs, one variable resistor and a 9 volt battery pigtail (not in pics). A reference is on the back of the board to help with identifying the parts. Note that the reference lists the transistors as 2N4401, but I may substitute other NPNs as needed depending on availability. (2N3904, 2N2222, etc) The circuit is a modern astable version of the Flip Flop circuit. Once power is applied to the power pads (9 volts dc provided by you), the LEDs should blink alternately. While this is a simple circuit, it has several variations with many uses. Look it up! :) Note: this kit is not designed to teach you how to solder, but to practice what you've learned. Experience with soldering equipment is required. Shoot me a message if the listing shows less quantity available than you are planning to purchase.I usually have the parts on hand and can have more ready in a short time. Thanks for looking. Check out my other kits! More to come...