The Guardian Cap does double duty. First, It gives you a chimney cap with a screen, making it a great choice for relining jobs. Second, it makes a great replacement cap for solid-pack, factory-built chimneys. It secures to both chimney liners and solid-pack, and factory-built chimneys by sliding inside with a tight friction fit, All Guardian Caps have a 4 5/8" high collar and come preassembled ∙ 304 or 316-alloy ∙ Use with liners and solid-pack factory-built chimneys ∙ UL Listed with HomeSaver Liner ∙ 3/4" and 5/8" Mesh ∙Lifetime Warranty