I understand that Woodhead outlets have a higher and purer copper content than any hospital grade outlet. I understand that an audio dealer supposedly did extensive listening testing of some 40 or more different plugs and believes Woodhead to be superior. They sell retail for over $40 which is nearly double the Hubbel hospital grade. And apparently the Woodhead are not hospital grade since, for at least one thing, they do not have the plug retension properies that are required. Has anyone heard these? AlbertPorter?