5/8" Stainless Steel Mesh 8" Wide x 96" Long - California and some other areas require a 5/8" spark arrester to fulfill regulatory codes. To make such a reduced spark arrestor that does not clog, chimney cap manufactures follow the interpretation that a sphere larger than 1/2" in diameter should not penetrate the screen. This is wording the National Fire Protection Association uses, as well as the one being referred to by several California localities. Thus, the spark arrestor screens measure 5/8" from center to center, but still won't let a 1/2" sphere through. This makes them somewhat clog resistant while still meeting major code interpretations. Yep, it's the same screen that's used in the construction of Gelco Chimney Caps. Stainless Steel Mesh is for those chimneys with decorative stone or brick tops where you cannot install a traditional chimney cap. This mesh is made of heavy, 18-ga. stainless steel.