Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: What are the dimensions of the shelf?
Document: This is a very cool shelf adds something new and unique to my poker room, I love it. Just what I needed.
It looks great under a wall mounted tv . The only down size was shipping was a bit much. Wish that it had room for a 3rd shelf
I love this mount. Looks great on my wall. I have it mounted under my 50 inch tv. With my sound bar on the top shelf, cable box and blu ray player on the second shelf
This is a very solid and stylish A/V shelf. Mounting it was a bit tricky - it's a bit unwieldy with the shelves folded out. Once it was up, the rest of the installation went smoothly.My only complaints are:1) The packaging is a bit of a mess. There were Styrofoam and fiberglass bits all over the place when I opened the box.
This is the second Omnimount wall shelf I've purchased, based on previous purchase, the ease of mounting and the use I've gotten from the first one which I installed in my bedroom, the second will be utilized in my under construction man cave (spare bedroom) beginning empty nesters.
That's easy enough to fix with a black marker or touch-up paint.One warning - there is a ~1&#34; gap in the black backplate underneath each of the shelves. If you mount the unit high enough, that gap will be noticeable (particularly if you mount it on a white wall).All in all, I'm very happy with the shelf, and it looks great on the wall.
Easy to install. I installed the Arlington DVFR4BL-1 behind this and it worked beautifully (much better than the single shelf due to a cross member blocking access to the outlets). With proper tools does not take long at all to install. Holds Dish Hopper, X-Box and Blu-Ray Player easily. The only thing I don't like it the available space for wires. It works but be careful of how much excess wire  you have.
I'm comfortable doing construction so I had to install additional studs in my wall to assure 35 lb weight capacity.I had to also build an additional painted black wood base which I placed underneath my reciever and on top the glass because the depth of the shelf is too short to include the feet of the receiver(because of the protruding wires in the rear). I made the base long enough to support the feet but a couple inches in from the front of the receiver so that you can't see it.
Well made, easy to install, and looks great in my family room. Just what I was looking for. Easily holds all of my accessories and keeps the cords hidden from view. It's a winner.
Well described and is a perfect addition to my living room. Conceals the cables well and holds well - nice and flush to the wall.
Answer: Bottom - 15 x 18.5Top - 12 x 18.5