Shelving seems to be pretty solid.  I did have to contact the manufacturer right away, because it is virtually impossible to use a shelf to attach the upper and lower vertical pieces.  The manufacturer sent metal sleeves that fit over the top of the lower vertical piece and the bottom of the upper vertical pieces (see photos).  Once in place, things were solid.  The main drawback is you can't mount a shelf in that spot.  Also, not all the ends of the vertical pieces were straight.  Some were cut at a slight angle.  Not a problem for me since it's on concrete, but if on wood or some other softer material, the ends will probably cut into the flooring.  Will also eventually replace the particle board shelving with plywood, since the particle board will most likely warp sooner or later.  All-in-all, though, decent shelving for the cost.