Recently upgraded my xenon bulbs on both my Z and wife's X. Both cars had less than 50,000 miles but we rarely drive with headlights set to auto (and my wife hates driving at night) so these should have decent life. FYI Z4 takes D2S, but throwing in the D1S in case you also have another car that may need em. Selling both pairs for $30 shipped if PayPal as gift.