A bouldering mat or crash pad is a small foam pad used for protection when bouldering. There are various sizes and makes, but the most common type is a folded mattress, 8 to 10 centimeters thick (3 to 4 inches), that when unfolded measures about 1 x 1.3 meters (3 x 4 feet). Bouldering pads often have shoulder straps so as to easily move it between boulders.