In the context of scene releases, a "PROPER" usually indicates a fix for a previous release that had technical issues. However, if you are looking for technical specs to ensure you have the right version, here is what that specific file signature entails: Technical Specifications 2160p (4K UHD)

Approximately 1 hour and 52 minutes, according to Amazon . Where to find associated "pieces"

The "proper piece" for a release with the filename usually refers to a NFO file or a specific subtitle file that matches the exact timing of that high-definition WEB-DL rip.