Product details:

The Flueblocker is a dense wool pad that seals and insulates the fireplor wood stove chimney. It can easily be installed and uninstalled many times. You MUST remove the Flueblocker before you light your fireplace. Cannot be used in functional vented gas log fireplace. Flueblocker is made with Herdwick wool at the Chimney Sheep facility in England. Model # FB12R Features: For round flues with a diameter of 11", 12" or 13". Prevents bad chimney odors and smells Reduces heating bills by stopping cold chimney drafts Stops birds, bats and bugs from entering the home through the chimney Can be trimmed to size with scissors Item Dimensions: 15" L x 15" W x 1" H.