i believe TECHNICALLY anything 5000k over is illegal and some in high 4k's but cops dont usually pull over for that stupid @$@$@$@$. any color over/under 4300k is wasting power. 4300k is the brightest possible which is why bmw and mercedes use it. 3000k on reg lights would get you pulled over easy because 3000k's are used for fog lights on the bottom while ur lows are on. also if u go to google 4300k has a straight line when car is next to a wall when anything over it like 5000k+ shines everywhere which are the kind that blind u when they are comming from the other way. 4300ks will only shine up to a normal cars hood in a perfect straight line when usual 6000k's are out of control and shine as high as stop lights even when on low beams which is why they are illegal. any higher than 4300k creates glare for oncomers. go to this website explains the 4100k vs the other ones. http://www.intellexual.net/hid.html