The Pergola was excellent quality and very easy to put together. You can even slide it to fit a slightly smaller space. I put it on Concrete and bought bases to screw into the concrete, using 3 ft 4x4 lumber piece inside and it worked well.  It is very stable and secure, and doesn't have any issues in strong winds.  The company was great to work with on one slightly damaged piece and immediately sent out a replacement.  I couldn't have ask for more.