We bought this to convert our Kalani Crib to a full size bed. As stated in the reviews, we purchased a standard 53” wide box spring. Upon initially assembly, the bed ended up being about 1” too narrow to support the box spring. I had read a handful of other reviewers who had stated the same thing but it seemed unlikely that nearly 700 other reviewers did not have this issue. We spent 3 days trying to figure out what was wrong, and eventually discovered that we had put the rails in upside down. There is nothing to specify in the assembly directions which way they go. So, when you assemble this bed with the Kalani crib, ensure the more narrow end of the rails are facing up. I hope this information saves someone the stress we went through trying to make this product work. Now that we have it installed correctly the bed is perfect.