A very high quality viewport window Cat.A #4 (Fig 1) has been installed at AS port.

This is the final Cat.A window installed; in other words, I completed the installation of Cat. A viewport windows at last. A long time has passed since the Cat A viewport windows were bought, and I like to celerate this silently. Today firstly I forgot where I stocked it and looked for; I found it was in the disiccator at the PSL room's entrance. At that time it was the only desiccator in the tunnel.
 

About the wedge; as shown in Fig 2 and 3, now the thickest side comes in the  minus-Y direction, which I directly confirmed to Somiya-san and Michimura-kun just before installing it for double checking; see also this document.

• Note 1: according to the package of the viewport (Fig 1), the arrow at the outer diameter points surface 1, which does not have the wedge. This is different from the description of the quotation at that time, but the same for the other very high quality viewport windows. Anyway, the same arrowing would be nice.
• Note 2: I firstly tried to use the original bolts (M8x30 or 35?) with the original washers, which were used to fix a blanck flange here, to fix the viewport, but it turned out that the screw length was too short for this new viewport and the washers were too large for the recesses on the new viewport. So I used M8x40 and smaller washers prepared.