These are absolutely the worst stools I could have bought they are completely rubbish.  I bought four in total and all have broken in exactly the same way (see photos).  I thought for the first one it might have a been a careless child but as all four chairs have snapped in the same way it has got to be a design fault.  We are a not a large family so they don't get that much use nor are we heavy/clumsy or careless.  Do not buy these!  I took a picture of the first one (indoors) with a view to sending it to Wayfair a few months ago but left it and now this last two weeks the others have broken are outside getting ready to go to the tip.  Essentially the plastic is not strong enough or secure to hold the legs in place.
Hopefully I might win £500 so I can replace them with something that will last longer than the 10 months we had these four!