The DLL size is increased mainly because of the new file icon sizes (256x256, 96x96, 48x48 and 32x32 pixels) in addition to 16x16 pixels and the bundled video converter (ffmpeg.exe) for generating thumbnails for any type of video file. Also other new features adds up. Note that, with the initial v4.0 the size was actually around 20MB and with v4.1.5 we reduced the size by 40% via making a custom build of ffmpeg.exe so that unused features were stripped as much as possible.