This more a floor liner than what I would classify as an actual tray, it's useful to protect the carpet. I have several plastic storage bins that I keep under the rear sets, this "tray" keeps them from sliding around.
Installation tip... after removing it from the shipping box and unrolling it, use a hair dryer to warm it up and you can use your hand/fingers to "iron" out the creases it will have from being folded over to fit in the box.