These highly versatile raisers work with furniture which has castors or legs, using the unique "doughnut" to grip-on to the furniture. This enables the raiser to become attached to the furniture without damaging it. Height adjustment is achieved by adding or removing sections of the raiser. No tools are required & the maximum user weight is 318kg per set of four. Accepts furniture legs measuring between: 20-38mm (D4637), 32-50mm (D4638) & 40-60mm (D4639)