The Cloud 9 Eco Cushion 15mm Artificial Grass Underlay is the ideal underlay for indoor and outdoor use in your garden and home! This underlay is also recommended for domestic use if laying artificial grass on hard surfaces such as concrete, patio, decking or balconies, creating a softer surface. The cushioned underlay allows the passage of water and does not hold moisture, so you will not be left with any puddling on your artificial grass.