Super bright LED Strips. These can be cut and joined every 5cm. They come in 1Meter segments, and you can direct wire them to 3S or 4S voltage, or to a 12v regulator.
I've tested them from 9.5v to 17v. They run very cool at 12v, and at 17v they get very warm if you're props are not running. I have tested them on for 30 minutes of 17v and they did not burn me ;)
I'm carrying Green, Red, Blue, Ice Blue, Purple, Yellow, Orange and Pink.
5watts per meter
There's a 1 in 5 chance that your strip will come pre-soldered with a wire, I prefer to DIY with a silicone jacketed motor wire, a dab of conformal coating, and a centimeter of heatshrink tubing.
Need 6S? I've got those too, in the Electronics/LED section, and I'm stocking even smaller 2.7mm wide 3S-4S strips too!