NRS Universal Kayak Block Grey Pair The two 14" wide, durable minicell foam blocks have molded channels that fit over your roof rack bars The V-shape cradles the hull of your kayak, protecting the boat and helping prevent side slip Traction pads prevent the blocks from sliding on the top of your vehicle If you don't have a roof rack, the Blocks can be placed directly on your vehicle's roof 14" L - V-shaped foam blocks, 5"W and 3"D (on ends)