All top-vent wall furnaces are designed to be vented through the roof with 4" oval double-wall metal pipe to maintain clearances in the limited stud wall space. This kit makes converting to round vent simple and easy.
If you're looking for the Williams 9901, the Williams 9929 is the new replacement.
Included in the Williams 9929 Box:
(1) Hold Down Plate
(1) Oval-to-Round Adaptor
(2) Ceiling Plate Spacer
(2) 4" Oval Pipe