natural ground protection boards 12mm thick for apron . 12mm thick ground access mats for apron-HDPE Ground 12m [] IN STOCK! - 4x8 Black Mats. Our ground protection mats made from 100% recycled high-density polyethylene (HDPE), can hold up to 100 tons and are tough enough to not break. Mats have cleats and textured tops to aid with helping