My knobs arrived yesterday. Solid machined aluminum, 30mm dia x 20mm high. Matte black finish with a little dimple on the face thats perfect for adding a drop of white paint on the tip of a toothpick.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Ffarm8.staticflickr.com%2F7322%2F9760840044_b4202e9a57_o.jpg&hash=e93cee30966269e551f9acba2710b76357714c77)
Put one on Crack and the other on Stereomour -
Found on ebay and 2 of them cost me a whole four dollars and seventy four cents. Including shipping all the way from China.
Amazing.