The diamond sanding strips grits are 60, 120, 220, 400, 800, 1800, 3500. You can buy the sanding block and individual sanding strips in the grits that you prefer. The Velcro Block and diamond sanding strips give you the option of using the sanding strips in two manners -
Use with the block for a rigid sanding surface or
Use without the block for a flexible sanding option.
The Velcro Block is $10. Each individual velcro diamond sanding strip is $19. If you purchase the set of 7 diamond sanding strips for $133 the Velcro Block is free.