The size of the small circuit board is 33mm x 25mm (approximately 1.30in x 0.98in). There is a blue adjustable resistor, two electrolytic capacitors and multiple surface mount components on the circuit board, including resistors and integrated circuits. The circuit board can be used to control the on and off of LED lights, meeting different usage requirements. This circuit board is a simple LED driver circuit that can change the current by adjusting the resistor, thereby controlling the brightness of the LED light. This circuit board is often used in model railways, toys or other occasions that require simple LED control. Date First Available March 25, 2021