Proline Decorative Concrete Systems RS350F 26" x 56" San Diego Flagstone Thinflex Concrete Stamp. San Diego, CA is home-sweet-home to our brand new flagstone. With 39.5 Inch stones, this pattern is sure to impress the neighbors. San Diego Flagstone pattern is able to rotate 360 deg with a natural fractured edge, you may not even know its decorative concrete. If you like large stones, check out the rest of our Grand Series, including the Grand garden stone and of course the Connors Quarry stone.