It is great concept of using recycled stryofoam. Unfortunately, there is limited quality control on the product. They are supposed to hold the tolerances +/- 1/8" for their dimensions, I was told by Dan. Not hardly. I had one block that was a full 11" wide. Over an 1" wider than specified. It was not uncommon for the blocks to be 1/4 -1/2" short in one direction or another. Made extremely hard to keep the build square and plumb with such crappy quality control. At the time when I was purchasing the product it came from a prison labor in Kingman. I glad they were helping the inmates but limited quality. Additionally, EF Block has not figured out how to mix their product properly before pouring it. I cut everything by hand (no power at the site) and every third or forth cut resulted in hitting a lump of cement. This alone cost me probable a week in extra time of building my project. Brought this up to Dan and he laughed about it. He called it 'Rastra nuts'. Apparently it was know issue that has not been resolved since it concept in the late 80's. I kept a bag full of the Rastra nuts and several samples of the Rastra nuts embedded in the block as proof of the issue. If you are doing this yourself make sure make sure when you grout don't grout more 4' high at a time. Otherwise you risk the possibilities of 'blowout'. Make sure the grout flows properly otherwise you will end up with voids. Major pain to fix. I would definitely look at other products on the market before I would ever use this again. On the positive side, I will say it has reasonable good insultation properties. It is not termite proof, they can still travel thru the product to find wood.