HOW TO INSTALL:

Rename the file from:

4x-UltraSharp.pt to: 4x-UltraSharp.pth

Copy the file 4x-UltraSharp.pth inside the folder: "\YOUR~STABLE~DIFFUSION~FOLDER\models\ESRGAN\")

Restart you Stable Diffusion

Now in "Extra Tab" you got the new upscaler