3"D, PelletVent Appliance Pipe Adapter, Used To Attach Outlet Allowing For Easy Pipe Connection, Must Seal Adapter To Appliance With High Temperature Sealant, Designed For Stoves That Burn Wood Pellets, Patent Pending Venting For Stoves & Inserts That Use Wood Pellets, UL Listed For 3" Clearance To Combustibles In USA & Canada.