9007 is a dual beam size used for the headlights. It is available in HID and LED conversion kits. When choosing HID set, you will have 3 options: Bi-Xenon, Low Xenon/High Halogen, and Single beam. Bi-Xenon and Low Xenon/High Halogen kits are dual beam kits so that they convert both high and low beams (2000-2005 Chevrolet Cavalier and 2005-2010 Chevrolet Cobalt). With Bi-Xenon kit you will have both beams Xenon. If you choose Low Xenon/High Halogen set the high beams will be the same like your factory Halogen lights. Single beam 9007 kit is usually used to convert headlights. In this case, two different kits are needed to upgrade both beams. All kits are available in 35W and 55W options. The latter produces 20% more light output.
If none of your lights come on, only one beam is working, or your high and low beams are reversed, you can try repinning the OEM connector in order to change 9007 kit to 9004.
All LED kits are dual beam. You can choose between LEDs with ETI and Cree Chips. The bulbs with ETI Chips are designed with silicone arc cover that allows better light emission. The bulbs have separate drivers to provide with the power cooling fan and chips. LED lights with Cree Chips do not have the drivers, as all the components are located in the bulb assembly. What is beneficial about this kit is an availability of blue and yellow color filters.