HETAS Approved 6” (150mm) 316 Grade Flexible Liner and Installation Kit (Our Ref: Kit 2). Approvals: HETAS and CA. Common problems including insufficient draw to power the stove, lack of heat output and leaking tar/smoke can all be rectified by re-lining the chimney with a Flexible Chimney Liner; an essential product when installing into an existing fireplace and chimney.