The DirectVent Pro 4 x 6-5/8 Inner Diameter Galvanized 9 Pipe Length is a component that is used in a typical venting installation. The DuraVent 9 direct vent pipe is designed for appliances tested and listed for direct vent. Features a fully unitized twist-lock construction in both 4 x6-5/8 and 5 x8 vent sizes. Use of sealant is optional unless specified by the appliance manufacturer. To calculate install length subtract 1 1/2” for each joint. No beads or hems. Black pipe lengths feature exterior laser-welded seams. DirectVent Pro features tight inner connections for superb performance with no gaskets or sealants required (unless specified by the appliance manufacturer). All black pipe lengths pipe extensions and elbows feature laser-welded outer wall seams for a sleek finish. Low-profile locks and no hems or beads allow for a beautiful product that looks elegant in any interior. DirectVent Pro is a unitized coaxial venting system designed for use with direct vent gas or propane stoves heaters and fireplaces.