Underglow.
i have the color change ones. i had them on my 06 SS and got a different set on my 09 SS/TC i only got pulled over 1 time for them on 1 interstate where i live and to this day thats the only place i dont turn mine on. anywhere else they never bother me. i really like mine though. i dont have any pics of them on my new car i'll try to get some soon.
Outside. It just didn't sit flush with the underside of the car. The only problem with that is you can see the bulb. I had painted the reverse bulb black so you couldent see the light source
Here are a few pics from start to finish

I taped off 50% of the bulb and painted it black

The light still shines off the back of the pinch weld so light is still seen around the bulb

This is a Befor

After
Here are a few pics from start to finish

I taped off 50% of the bulb and painted it black

The light still shines off the back of the pinch weld so light is still seen around the bulb

This is a Befor

After
go to www.ledglow.com they have the best price and quality neons imo
If you gonna get them, i recomend LED glow's kits. Youll find banners on the bottom of this site all the time. The kits I showed are all LED glow except the 1st pic of the silver SS. LED Glows kits all have wireless remotes so you dont have to drill any holes or wire any switches. You run the wires under your car to the trunk, in your spare tire well theres little plugs, just punch one out, put the wires in, and all the tubes go to a small box thats supplied wit the kit. Then theres just a red wire and a black wire for power and ground. Hook that up right to the battery as your already in the trunk, and there ya go. Comes with 2 keychain remotes with power buttons and controls for the patters. No switches or anything. And if you get the Interior kit for it, it all works off the same box and keychain. I recommend the 7 color though, because the 3 million kits actually have a large blue controller that you need to keep by the driver seat because the power button and the settings for the tube color and shade all have to be done manually. Stupid if you ask me. Plus with the 7 color kit, you can have 6 interior tubes and 4 underbody tubes, and you may be able to branch off of them with more. But that means 4 interior, and 1 under the hood and 1 trunk tube. That should be enough for anyone.
And my underbodies are no more because i guess i bottomed out and my front tube cracked and eventually got water in it. Still worked, but certain LED's wouldnt light. Eventually that shorted out the rest of the LED's for the other tubes and ruined them. If I were to install again I would just tuck the front tube up as high as I can. Dont put it below the intercooler like i did.
And my underbodies are no more because i guess i bottomed out and my front tube cracked and eventually got water in it. Still worked, but certain LED's wouldnt light. Eventually that shorted out the rest of the LED's for the other tubes and ruined them. If I were to install again I would just tuck the front tube up as high as I can. Dont put it below the intercooler like i did.
I am thouroughly amazed that this thread has made it more than a page without a "underglow is rice" comment. That's a major improvement for this site. Anyways, I always though underglow didn't look bad at all when done right. As Gestapo said, I would go color changing leds if I was doing underglow. That way if you change your mind about the color you can just change it later. Plus the wireless remote is an awesome feature to have. Tucking it up as far as you can is a good idea too so you don't break it.
























