This Unique insert adapter 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 accommodating a horizontal offset from 0 inches to 9 inches without the added clearance required for elbows. The top collar accepts M-Flex Chimney Liner or Premier Rigid Pipe. The Bottom of the collar will fit into most stoves that require a crimped connection. Easily attached with screws or rivets like all quality M-Flex Chimney Liner Components. Made in the U.S.A