This product is so simple to install, and fits perfectly, increasing the storage space in your 4Runner's door. It will securely hold whatever small quickly accessible items you can think of. I don't keep my phone in the door (although this product works great for that of course), but I like to keep a flashlight, small hand sanitizer bottle, and some other little odds and ends in there instead. Before I installed these inserts, the items would sometimes fall out when I shut the door, or a phone would bounce out a few times while driving. Not any more, these inserts do their job great!
The inserts are made with a very high quality plastic, with double sided tape on the back that securely holds them in place. The design makes for a perfect fit in each door, and the "tray" part has a rigid/rougher feel instead of smooth plastic to keep items from sliding around. I had some other protective rubber door inserts that I was able to easily cut down to the same size of the smartphone door insert and use both, which I highly suggest because they both have different functions. The smartphone inserts increase the height and usability of the storage space, and the rubber inserts protect the smartphone inserts from getting dirty and gunky.
Probably one of the easiest and most bang for your buck mods you can do to your 4Runner.