Napoleon 4"x7" Coupler Kit (4"/7" Venting) safety-barrier it is too dry

it is too dry

On what kind of walls can I mount my fireplace onto

Model KCS3611DS Product Size 36" Fuel Type Natural Gas or Propane Vent Type Vented Weight 162 lbs Number of Logs in Set  11 Fireplace Dimension Depth 21" x Fronth Width 42" x Back Width 42"

VRT4542WS Product Type Vent-Free Gas Fireplace Framing Width

Napoleon 4"x7" Coupler Kit (4"/7" Venting) safety-barrier it is too dryNapoleon W175 0195 4 Inch x 7 Inch Coupler for Flexible Direct Vent For use with 4 Inch x 7 Inch Flexible Direct Vent Connects two 4 Inch x 7 Inch flexible direct vent liners Coupler Kits to connect intake and exhaust direct vent Freedom Flex pipes