Great  portable units to help extend the growing season from early spring to late fall. Easy to move from one part of the garden to the other. Frame rails are all metal but the connector joints are plastic, which I do not like. These plastic joints will break down become brittle and break down before the rest of the greenhouse tunnel. Could be replaced by metal  pipe joints, but this is just an added expense. Also,all the doors, entry points are all on one side, and it would be nice if one of the end doors could be on the other side to aid through ventilation. Other than that decent ,functional units.