Olfa’s patented 1.5mm thick self-healing mats are designed to take the wear and tear that your rotary cutting blades dish out.  Self-healing means the mat will not get cuts, grooves or nicks on the surface, all of which can make your cutting less than perfect.  Yellow grid lines help you with measuring on one side, solid green on the opposite side for general cutting.  To prevent warping, rotary mats must be stored flat.