1.Plastic 2.Package includes 4 pcs small risers for elevating 3 inches and 4 pcs large risers for elevating 5 inches. They can be used alone or stacked to elevate a sofa or bed by up to 8 inches. 3.Furniture risers can creates additional storage space by improving the height of furniture, so you can store more sundries, luggage or storage boxes. Also it helps sweeping robot enter to clean your under bed. 4.Bed raisers are made of high quality plastic, strong and sturdy. They can handle heavy duty furniture up to 2200 lbs. The top equipped with a shock-absorbing pad for protecting your furniture, withstanding pressure and reducing noise. 5.These stackable risers are suitable for beds, couches, desks, chairs, recliner, cabinets, tables, sofas, especially those with wheels or rectangular legs. Also it can easily solve the problem of raising the furniture who without legs. 6.Easy-Install, you can put these heavy duty risers under furniture legs in mere minutes. And the bottom with a soft rubber pad for protecting the floor from scratches.