This unique insert adapter that allows a front-to-back or a side-to-side adjustment in the firebox. The two piece design allows it to slide to adjust the center-to-center distance of the collars. This accommodates a horizontal offset from 0" to 9" without the added clearance required for elbows. The top collar accepts OD flex liner or rigid pipe. It will also accept ID pipe in conjunction with a coupler. The bottom collar will fit into most stoves that require a crimped connection. Attaches with screws or rivets like most liner or pipe.