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.