Mine are 36" 3/8" long. Also, they are 1/2" too short. Put them on the side rails for the bed setup, put some weight on them and they fall through. The factory is making me new table tops 1/2" longer under warranty.
When you do your walk through, put a top on the supports, slide it to one side and see how much of a gap you have.
It's a known problem and you can read about it in this thread as well as some other issues to watch for.
http://www.airforums.com/forums/f516...6u-139457.html
You'll love this 26U layout with the twins.
To me....the width is 19"3/8" The length is 36"3/8"