Two takes on the same idea: a Japanese-style cup with no handle, made to be held. You get the warmth of the drink through the stoneware, which is half the point of drinking this way.
The original Koto has a smooth matte glaze and sits at 165ml - right for a flat white, cortado, matcha or a cup of tea. The Koto 220 is a little larger and a little glossier, with a reactive glaze that fades one colour into another down the side. Because it's reactive, no two come out the same, so yours won't quite match the photo.
Pick the size and finish that suits how you drink. Both come in a range of colours, and the 220 as a boxed set of four if you're buying a gift.