The seat and legs are separate - this is assembly required but it's like IKEA where they give you everything you'd need. Make sure to take all the plastic wrap off the legs before you assemble. It was very easy to put together, though I did have to think for a minute.
Once assembled, the chairs seem sturdy enough for my purposes (dining and misc seating) and the plastic seats have some give so that a person can lean back in the chair a little. Overall I'm pretty happy with these for the price.