8" DuraVent DuraLiner Masonry Thimble with Slip Connector 8DLR-MTSC1 This masonry thimble with slip connector is used to penetrate masonry chimney to allow connection of DuraBlack or DVL to DuraLiner. Adaptor must be used to attach the connector pipe to the masonry thimble. Use with DuraVent factory-built chimneys 430-alloy stainless inner wall aluminized steel outer wall 1" outer diameter Reduces clearances from 18" to 6" for walls Reduces clearances from 18" to 8" for ceilings Sturdy construction to ensure long-lasting durability Creates a tight secure connection in your venting system .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.