A 2008 Lexus GS300 smart key will need to be programmed to your vehicle before it will work for you. Programming can only be done at a local automotive locksmith or dealership, where they will also be able to cut the emergency key blade to match your original. There are no onboard programming instructions for 2008 Lexus GS300 smart keys. They can only be programmed using special diagnostic equipment. This smart key comes with a brand new battery and is tested for functionality before sending. This Smart key comes with 4 buttons and if you look on the back of the unit, you may see some of these numbers: HYQ14AAB - 1551A-14AAB - 315 Mhz . Use these numbers to confirm that your Smart key will match this product and that it will work for your vehicle.