Bests & Worsts Reviews from Amazon

I don't know what black magic they got in there, but the bulb works in both standard style socket and CK style socket. But in both cases, it will only work one way. So if yours isn't working properly, flip it! Looking at the 7443 socket from above, If you have a standard socket, insert the bulb such that Philips Logo points up with the two ground contacts on the left. Ground Tail ------------------ Philips Logo No Logo ------------------ Ground Brake If you have CK socket, insert the bulb such that Philips Logo points towards the two ground contacts: Brake Tail ------------------ No Logo Philips Logo ------------------ Ground Ground I poked at the contacts with a multimeter and 12V power/ground a bunch of different ways and it's extremely interesting to note that you can short either the left two (standard grounds) or the bottom two (CK grounds), and the bulb still functions perfectly, as long as the shorted pins are both grounded. I have mine working in 2015 Subaru Impreza, which uses CK wiring. It's obvious when you take the socket out of the enclosure because the back of the socket shows the single ground wire on one side of the socket. I used Canon 40D in manual mode (fixed aperture, shutter speed, and ISO) and analyzed the luminosity of the wall reflection images using histogram function. Image came out generally dark, but I don't think that would make any difference. Mean luminosity for each were: Incandescent Tail: 1.47 Incandescent Brake: 4.69 Philips LED Tail: 1.36 Philips LED Brake: 3.03 So in my test, LED came out slightly dimmer overall. I don't think it's a big deal, though. And since my car is fairly new, the bulbs are new, too, and so I assume the incandescent bulbs would've gotten dimmer faster over time than the LEDs. And the instant ON nature of the LEDs are an added bonus, too. Update 2015-12-08: I think the luminosity comparison is not really valid because incandescent bulbs outputs full spectrum, whereas LEDs only outputs red wavelength. Some of the non-red light will make it out, even though there is the red plastic lens filter, and that will affect the incandescent bulb's luminosity reading. In the end, I do not believe the incandescent bulbs are brighter than the LEDs as brake lights. The only thing that matters for me is that these LED bulbs meet the DOT requirement, and they're working great for me.