Use for offsets around obstructions such as rafters, ridgepoles, or joists. May have up to two pairs of elbows, if needed. Offsets greater than 30° are not permitted in accordance to UL 103 standards. Elbows swivel 360° at base (angles are not adjustable). A pair of elbows is required to return an offset chimney back to vertical. Galvalume exterior wall.