Osram Xenarc D1S Xenon 4300K Bulb to fit the most vehicles with this bulb as fitted standard. (Also suitable as a replacement for Philips Brand) It is recommended that these bulbs are replaced in pairs, as discolouration may occur between the life of an older bulb and a new one. It is also recommended by many manufacturers to replace Xenon headlight bulbs every 2 years to ensure optimum lighting performance.