I found this base to be very sturdy and the wheels easy to roll even on carpet. Two of the wheels have locks which worked very well. I bought 30 lipless stackable trays and found the base to easily support them. I am going to be buying another base and 20 more lipless trays to finish putting all my paper in. I love that they don't take up much room.
I read the other reviews and I decided this base was exactly what I wanted; sturdy and durable. I was not disappointed. Tray is very sturdy and so far has worked out great!
The base is excellent for the Stacking Trays. All I had to do was pop the wheels on the base and then stack the paper trays on top. There are wheel locks for the base too.