These work great with LED lights, they have a distinct clicking sound that makes you switch off the turning light manually if they don't come off automatically, it will also make your light flash at a faster rate than normal. I ordered two of these for my '65 Mustang with a Ron Francis aftermarket wiring kit. Remember to order two of them if you have a separate hazard/emergency flasher relay. There was no need for the HW2812 POLARITY REVERSE FOR LED FLASHER in my car with the RF wiring kit, but am not sure how it's like in the original cars. I ordered two of them too just in case.