Risers are flexible foam components that elevate track and roads above the base. Elevating with Risers allows for dramatic scenery possibilities, such as valleys and water areas, without cutting into the base. Use at least 2" Risers to elevate the track. For a dramatic landscape, use 4" Risers to give maximum elevation for steep relief, rivers and valleys. Risers are available in 1/2", 3/4", 1", 2" and 4" heights. They easily flex to form curves. You will need the same number of feet in Risers. All Risers are 2 1/2" wide and 24" long. Purchase the SubTerrain Manual for additional information on how to use the foam system.