look for great feedback comments from any buyers, ask the seller if you can contact anyone that bought from them.
look for brand names and companies that you can contact directly if you have fitment issues. e-bay sellers, most, don't know feces from pledge when it comes to what they sell and can't help most of the time if you need help.
This is just from my personal experience with them, so you guys really need to make your own opinions from your own experiences ( this is meant as a disclaimer to those e-bayers that are knowledgeable about their products)