The Superior 9 Vertical Firestop (Flex) - 10 pack SF4.5VF-10 by Superior Fireplaces is a crucial component for ensuring the safe and efficient installation of flex chimney liners. These firestops are designed to prevent the spread of fire while allowing your flex liner to pass through walls or ceilings, providing a secure seal. This 10 pack ensures you have an ample supply for multiple installations or future replacements. Trust in Superior Fireplaces for high-quality, reliable products to meet your chimney system needs. Safeguard your home and loved ones with the Superior 9 Vertical Firestop (Flex) - 10 pack SF4.5VF-10.