You need 9007. I've heard from people that have used Silverstars and have said they were not bright at all. Use Phillips Blue Vision for $13/ea. Don't go by the name they do not light up blue but a bright white.
Silverstars are ok, i have found them to be the brightest light. I had stock ones, then blue ones but then tinted my winshield and couldnt see at night that good but the silverstars made me see again.