Always support the official release. Buy the 4K disc or digital license to own the film legally, then use this open matte version as a companion piece for the ultimate collector's library. Have you compared the open matte to the Blu-ray? Share your screenshots and aspect ratio comparisons in the forums.
The movie was finished at a 2K digital intermediate (DI). Native 4K releases of 300 are upscales, not true 4K scans. Worse, the 4K HDR versions often apply excessive DNR (Digital Noise Reduction) and edge sharpening, which ruins the film’s signature gritty, grainy texture. 300 2006 open matte 1080p webdl x265 hevc 1 best
If you own a 55-inch or larger 4K TV, the upscaling done by your TV's internal processor on this file will look superior to the native 4K disc. You will see the blood spray. You will see the sweat on the Immortals' masks. And most importantly, you will see the full vertical height of the Persian arrows blotting out the sun. Always support the official release