When properly installed/seated, the extended eyecup is not likely to fall off. It's actually somewhat difficult to remove. Look closely at the photo below. The Fuji extended eyecup has two small plastic tabs on the bottom edge that clip in firmly below the viewfinder. This helps keep the extended cup from wobbling around or sliding off... and also makes it seemingly more difficult to remove. To remove, pull out on the bottom of the extended eyecup far enough to release the clips, then push upwards to remove.