Well, a couple of days ago the SilverStar Ultra low beam on the drivers side went out. So, I thought I would put in one zXe on the right side and put the Ultra on the left side. Found the zXe (XENON) lights at PepBoys for $59 + tax, and they only came in pairs. I installed them yesterday afternoon, so I had to wait until it got dark to notice any difference. The difference that I notice with the zXe over the Ultra is brighter low beams and more light on high beams. Hope they last a while.