Two mills in one, one for pepper, one for salt. And so easy to use; twist the top clockwise for pepper, turn it counterclockwise for salt. Both of the grinding mechanisms are non-corrosive ceramic, and both are easily, and individually, adjustable from the bottom, letting you go from fine to coarse in seconds. The Twin mill is easy to fill, too; just lift the top straight off to reveal large fill openings for salt and pepper. The Twin mill is made of stainless steel and acrylic, with a silicone grip ring. 4.5" high, 2.75" in diameter.