I have Multiple Sclerosis and I am an avid gardener.  When I discovered these reasonably priced 4 x 4 units I was so happy! This is just what I needed.  I bought 3 boxes of 3 each but their was only enough 2 high clips for 1 double unit in each box. I called customer service and the  representative was very helpful.  He is sending me a bag of 48 clips for double-deck units.  I am so happy!  I plan on buying 12 more units next year to make more raised beds.