This is the premier chimney cap for solving common, wind-related draft problems. Wind problems often occur for homes that have hills, mountains, tall trees or taller buildings in the vicinity. This cap also functions as a conventional chimney cap by protecting the chimney from rain, snow, debris, and animals. Designed specifically for oceanic environments, designed to protect against rust and erosion that othercaps crumble to. Made of 316 stainless steel. Made to fit round chimney liner and Class A solid pack chimneys. This Model works with the following types of chimneys: Single Wall Chimney Liner, Solid Pack Class A Chimney, B Vent, and Round Terra Cotta Flues Features For round chimney flue Protect your chimney from the elements Designed to work with Class A chimney components Specifically designed to combat wind related drafting issues Specifications Item Number VSM-03 Model Vacu Stack VSM Lid Size 13" Inner Diameter 3" Material Marine Grade T316 Stainless Steel Warranty Limited Lifetime Warranty Videos