The outside of the fan tray measures 500mm x 147mm (19 3/4" x 5 3/4"). The frame is 2mm thick.
If you look at the image carefully, you'll see that there's a label at the top. I added that because I kept getting the orientation of the tray reversed when mounting fans. You may not need it ... but I found it helpful.
The front tray will only fit in the case one way - you can't reverse it or flip it. It's 25mm deep - so just deep enough for a fan. It's not deep enough for a radiator - if you were thinking of mounting the radiator on the outside.