Yellow tinted, clear LED in T-1 package (3mm). Max. current (continuous) is 20mA, resulting in 2.0-2.1V forward voltage. LEDs are operated at constant current, not voltage! It is necessary, to limit the LED forward current with a resistor. The value of the resistor is easy to calculate following Ohm’s law: R = U / I. For example, on a 12V power supply, U = 12-2 = 10V, I = 0.02A. The resistor in this circuit should not be less than 10 / 0.02 = 500 Ohm (for max. brightness). For battery operated applications, you should consider a much lower LED current, for example 3mA (equals 3.3kOhm on 12V).