6024, which is a 12 volt 7" halogen bulb. I would suggest going ahead and replacing both, usually when one goes, the other isn't far behind.
http://www.oreillyauto.com/site/c/detail/SYL0/H6024.oap?pt=01576&ppt=C0010

Last edited by LONGBOX55; 07/18/2016 11:51 PM. Reason: link to part number added

Bill Burmeister