Hi Daksy,From the install manual...
View attachment 269008
Here is the COMPLETE manual:
Table Of Contents - Majestic 33BDVR Installation Instructions And Homeowner's Manual [Page 2]
View and Download Majestic 33BDVR installation instructions and homeowner's manual online. 33BDVR indoor fireplace pdf manual download. Table of Contents: Installation & Operating Instructions - Page 3; Fireplace Dimensions - Page 4; Clearance To Combustibles - Page 5; Framing And...www.manualslib.com
The manual tells you what vent pipe is approved for use with this unit.
You cannot use any other. Majestic is now owned by Hearth & Home Technologies.
Try to get the venting thru one of their dealers.