Quality is disappointing: it just doesn't feel very solid. More significantly one of the pre-screwed holes for the bolt fixing the back to an arm was not perfectly aligned with the bolt hole so the bolt had to be screwed it at a slight angle. Consequently neither it nor its neighbouring bolt could then be completely tightened: the bolt just kept going round and round. It is likely that I will have to use an extra screw on each side to improve the fit which then makes dismantling for storage or treatment more problematical.