A few of our new products such as the Box Baffles, are designed with a 3" empty cavity.
We ship the product flat and unassembled. The end user or contractor has the opportunity to insert a substrate such as Rockwool Safe'n Sound, this will increase the NRC to 1.05, as per the Rockwool documentation.
Our yet to be released Box Cloud, Box Panel will also allow for Roxul to be installed in their cavities. These products will also allow up to 6" of Roxul to be installed. With 6" of Rockwool, a 1.15 NRC can be achieved as per the Rockwool documentation.