Perfectly flat machined surface. Hard surface tension. Perfect flat sanding surfaces. Flexible. Patented This block is designed for sanding and prep work. It allows for easy use and much improved durability and firmness. H-1/2", W-2 1/2", L-5 3/8". Finally a small scruff pad that isn't flimsy. A professional hand pad that you can really sand with. Its increased density above the original Dura-Block, allows for firm but contoured sanding.