I installed a 2.75" 1550 nm AR Coated Viewport on the Laser Filter Cavity (LFC) Output Vacuum Cube. I tightened the bolts to 10.7 Nm. 9.6 Nm was not enough to get a full steel to steel contact. I checked the other viewport I installed, and I could see a bit of a gap. I therefore tightened those bolts to 10.7 Nm as well and the gap reduced in size. Other than the hose from the turbo pump to the scroll pump, the LFC should be completely sealed and ready to be pumped out.