According to this standard, the diameter of cylindrical civil coal can only have three specifications: 85 mm, 90 mm and 95 mm; There are also three specifications for height: 70 mm, 75 mm and 80 mm; The opening diameter is 12mm.

　　Coal balls are generally mechanical, shaped like ginkgo and as big as walnuts. The manufacturing method is as follows: the two rollers are driven by power to rotate relatively, and there are corresponding hemispherical dimples on the two rollers. When the coal powder, loess and water are evenly stirred according to a proper proportion, they are added from the upper part of the rollers and squeezed into a sphere by the corresponding two dimples.

　　In general, the diameter of coal balls is 100mm, the height is 75mm, the aperture is 14mm and the number of holes is 12.