This Fenchel Shades lamp shade has a top diameter of 11 inches, a bottom diameter of 17 inches, and a slant height of 13 inches. The vertical height of this shade is about 12.65 inches This attachment is called a washer attachment and is nickel in color. It is also known as a spider attachment. If your lamp has a harp, then you will generally need a washer attachment. The hole size (inner-dimension) of a washer attachment measures slightly under 1/2 inch. The drop on this particular attachment is 1/2 inch. That means, it recesses about 1/2 inch below the top of the lamp shade.