Me also for a big closet and wonder if they’re preassembled
They are not pre-assembled. I have a couple of the earlier versions, and while they’re a bit of a PITA to put together, they seem to be reasonably well made. Assembly instructions can be found on the manufacturer web site - scroll down to the Euro Quick-2-Connect pieces if you want to get a preview.
Slightly different color and drawer configuration, but same company and cheaper:
I don’t think that one has the adjustable drawer arrangement feature.
The two we bought are in the landfill. Unless they are improved, the bottom of each drawer sags under even modest weight and slips out of the grooves. If you are planning on storing reams of paper, etc. you may want to reconsider.
What a piece of junk!
No screws or nails to hold the drawers together! Pull the drawer out of the cabinet and the front comes off the sides. I have one of these from the same company I bought a few years ago and it had all the hardware to hold the drawers together. They cheeped out big time!!