Thank you for your question on the model 634 roof cap. Please contact our Customer Service Department at 800-558-1711 for assistance.

The 634M is the same roof cap except for use with a 6” round duct. You may want to consider the 634M if you haven’t already made your purchase. The 634 is for 3 ¼” x 10” or up to 8” round duct size. If you have the 634, the ducting can be installed so the pipe is just on the inside of the roof cap. You can put a foam seal around the pipe and the cap for the difference in size. Please contact technical support at 1-800-637-1453 for more assistance.