Returned the "el -cheapo" file for this one. Unit is solid smooth running has anti-stopover counter weight and rolls on hidden casters. Very pleased. So glad I returned the cheap unit.
Overall quality is excellent. It stands up to everyday use. My two negative comments are: 1) the unit tends to roll forward because you can't lock the casters. It is quite bothersome when you have one of the drawers out and it starts to roll foward and 2) you have to be very careful when opening the top drawer because the cabinet tips forward. I had to put some small pieces of wood in front of the front casters so it wouldn't roll. It would be helpful to have some type of counterbalance on the back so the cabinet does not tip so easily.
First one came with wheels attached. Second one didn't. Fortunately I make it a habit to have the store unpack it (I used the ship to store option). I complained and a salesman found a screwdriver and put the wheels. It didn't seem difficult but when it says "factory installed casters" that's what I expect. I wouldn't store money or other valuables in these but the work fine for files.