This little tester can test any 20ma LED (any color) without the need for a current limiting resistor. Just snap the tester on a standard 9-volt battery and start testing.
Accidental reverse connection will not harm LED. Accidental shorting of test clips will not harm tester.
Includes on-board solder pads (with holes) for resistors to experiment with LED brightness changes. Can also be used as a simple power source for small lighting projects.