There has been some comments coming back in that although the shields have been installed, there is still some leakage. On the 2 and 3 inch vents this should not be possible as the internal componants have sufficient clearence to compensate in the event the vent is not directly under the internal pipe. However, the smaller 1 1/2 inch vent may require confirmation that the internal pipe is directly over the vent inlet as there is only a 1/4 inch difference in diameter. So when installing these on the smaller vents, make sure you look down the shield and confirm its direcly over the vent inlet. This will stop any leakage.