What can I say? They're feet, they work, they look good.
They're easy to fit, with an opening that is fairly generous on the size of both screw thread and screw head that you use. They are firm rubber, but don't seem to chip, split, or crack like some of the harder feet do, and they don't sag and deform like the softer ones.
These ones are well sized, ideal for a medium sized amplifier or cabinet.