Unfortunately, this acoustic boot is no longer available as a separate item. Here is the link to the Acoustic Boot kit which comes with the two neoprene rings to adapt to this size:

Acoustic Boot Kit

• 4" x 4" x 8"
• High Temperature silicone rubber
• Wire reinforced

See Replacement:

• This item has been replaced by Acoustic Boot 02771000

Roberts-Gordon, LLC original parts. Roberts-Gordon, the world leader in infrared heating, headquartered in Buffalo, NY. With an extensive representative network in the United States, Canada, and across the world.