From the manufacturer:
Dritz-Omnigrid Mat 18x24 - Omnigrid mats have several unique features that quilters appreciate: One side features a medium green background with bright yellow grid lines and the other side features a solid grey without grid lines. Both sides feature a forgiving surface and will not damage your rotary cutter. The grids on these mats feature inch markings to the 1/8 inch and a full surface grid with 45 degree angles as well. Mat measures 18.75x24.75 inches with an 18X24 inch grid. Imported.
Dritz-Omnigrid Double-Sided Mat 12x18 - This self-healing cutting mat features grids and markings in both inches and centimeters-- one on each side. The inch side has a 12x18 inch grid spaced every 1 inch with 1/8 inch increments on the edge rulers. The centimeter side has a 30x45cm grid spaced every 1cm with .5cm increments on the edge rulers. Both sides also have 45-degree angles lines included. Overall dimensions of the mat are 12.75x18.75 inches. Each package contains one mat. Imported.