Although they look the same, concrete blcks come in all types and sizes. They can come in 4 inch, 6 inch, or 8 inch. They can also come in 10, 12, or 24 inch. Then, once you have the size, there are all kinds of different shapes and styles. For example, for 10 inch, there is half sash 10x8x16, stretcher/corner 10x8x16, and Pier Block 10x8x16. You can find all that information here:
. http://www.westbrookblock.com/products/sizes.htm.
