Utilizing Natural Rubber Open Cell Sponge hatch packing, an additional 1/4" thick layer of Cloth Inserted Rubber laminated into the open cell platform provides a very sturdy base. The dome of Open Cell Sponge creates a lively sealing area, and the entire section is completely weatherproofed by a tough Nylon inserted Neoprene jacket, which provides furthrer tear & abrasion resistance. All together a long-lasting and weather resistant seal !!