The Martelli Round-About 3-piece set includes the Round-About base, mat, and iron top. The base rotates on twenty-four stainless steel ball bearings. The mat is 12″ in diameter with the Martelli get-a-grip material on the backside of it. This means it will lock into the base or can be used in a stationary manner. The iron top also has the get-a-grip material on it (under the cover and a layer of 80/20 batting) so that it reflects the heat back into the material you are ironing. NOTE: WHEN USING THE IRONING TOP WITH THE 3PC ROUND-A-BOUT SET BE SURE TO REMOVE THE ROUND-A-BOUT MAT AND USE THE IRONING TOP ON THE ROUND-A-BOUT BASE ONLY AS HEAT FROM THE IRON CAN WARP THE ROUND-A-BOUT MAT.