6" DuraVent DuraLiner Adjustable Sleeve 6DLR-AS 6" DuraLiner Adjustable Sleeve is used for inserts with rear exhaust outlets. Sleeve adjusts from 8 1â„2†to 12â€. Diameter: 6" Length (adjustable): 8 1/2" to 12" Sturdy construction for long-lasting durability .016†304 stainless steel inner liner. Rigid relining pipe: double-walled with 304 stainless steel inner and galvalume outer. Factory insulated between inner and outer walls.