The chairs look nice and are fairly comfortable for the price. They are quick to assemble too, though I would note that the lever on one of the chairs was not capable of adjusting the height of the seat post. Fortunately, a quick torque was enough to bend the lever into shape and render it functional. I will simply chalk that up to possible shipping damage and conveniently look the other way.
The one inexcusable structural flaw in the design is how the backrest/arm bar is attached to the chair. Since the chairs are high up, people naturally tend to use the arm bar to help hoist themselves up into the seat. Paired with the foot bar, the arm bar is charged with supporting about half the person's weight while mounting or dismounting the chair. Rather than being bolted to something secure - like the metal plate which bolts the seat to the seat post - the arm bar is simply screwed into the particle board that constitutes the bottom of the seat cushion. Consequently, as people get in and out of chair they gradually strip the screws from the cheap wood. If you have small children, this can mean random bolts on the floor for them to pick up and curiously ingest. If you have guests, this can mean an impromptu visit to the floor while announcing the arrival of gravity as your social's guest of honor.
If you happen to have access to a metal fabrication facility - which who doesn't nowadays? - you can quite simply cut, drill, and tap a metal plate to meet the structural needs of the chair. If you plan on actually using these chairs - i.e. they will not just sit in the corner and look pretty - I would highly recommend this route as it will transform them from the overly cheap chairs you did not realize you were buying, into the standard fair, cheap chairs you thought you spent your money on. Even simpler would be to just buy a different make.
Matisse Company, I thumb my nose at you for inexcusable structural designs. Local metal fabricator, I applaud your assistance in rendering my chairs structurally sound for the mere added cost of $8.00 per chair. Matisse, if a fabricator can interrupt production and upgrade my chairs for $16.00, I would wager that you could simply implement this fix for a negligible cost.