The Forever 5/8 in. Mesh Spark Arrestor Cap 10 in. x 17 in. stainless steel. Superior animal proof oval hole mesh prevents creosote build up.17 in. x 24 in. 24-gauge hood, 20-gauge one piece base with built in 5/8 in., 8 in. high mesh screening. Adjustable will fit flue sizes from: 7 in. x 16-1/2 in. to 11 in. x 18-1/2 in. This cap conforms to California spark arrestor codes. Copper and custom sizes are also available.