The phrase "slimmer taillights" means that the lights at the back of a vehicle are thinner or narrower than before.
Sentences with «slimmer taillights»
A strong character line follows the tip of the headlight all the way around the back, where it's met with slim taillights connected by a trim strip. (cnet.com)
In back, expect slimmer taillights and further shiny trim detailing. (topspeed.com)
Curves and flowing lines are consistent throughout the sheet metal, including a rear end that features slim taillights in the form of a sequential L motif. (lexus-int.com)