Upon arrival, I saw that the whole thing was FLAT PACKED. You have to bend the drawers into the right shape (not too difficult - be careful they could snap) and then use little metal tabs to secure them. I don't use it on wheels as I bought these drawers to sit my desktop PC on. It does the job well and is sturdy.
The instructions are really poor and you are left to figure out which bit goes where, to be honest. If they had put the usual - this part is 1 and goes into slot 1 it would be so much better.
I can't complain, I do really like them and they have secured all my stuff and sits my PC on it.