Big Hole. 304 Stainless. The black color is an electrolytic process, like electroplating but with lacquer instead of metal. "In electrophoretic lacquering, the addition or subtraction of electrons reduces or oxidizes a soluble organic molecule into an insoluble molecule on the component being coated." Aren't you glad you asked.

8mm x 7mm Hole size is approx. 3mm. By the pack of 20.