mination where the use of a firestop or wall thimble reduces clearance to 1 -112' (38mm). Horizontal Top' 3" (76mm)' Horizontal Side 2 " (51mm) Horizontal Bottom 2" (51mm) Vertical Vent 2" (51mm) Below are the recommended framing dimensions (inside measurements) for the 4" x 6-5/8' rigid vent terminations