Installs quickly and eliminates need for using individual firestops. Round shielding acts as a radiation shield and provides the required 2" air space clearance to combustibles. The 2 sections telescope to accommodate 6" to 11" wall thickness. The hole opening in the faceplate for No. 206463 is 8.25"; for No. 207463 - 9.25"; and No. 208463 - 10.25".