Did you get resistors as well? I've always wanted switchback bulbs but I'm not certain that the light output, or rather if the color would be output correctly with my ion headlights.
Tested out the lights... They are very bright and they work perfect. Only drawback is that the color doesn't match my projector headlights or my fogs (5k).
I didn't install resistors, just changed the flasher unit to led one.