It is made by a technique called rapid cooling reduction from a high temperature of 1200 degrees into rice husks. The areas such as the back side that are not covered with pine ash are black and have an interesting burn. I think that the contrast between the red straw inside and the gray body was burnt in a calm sake set.
size
Length 7 cm Width 7 cm Height 3.5 cm
Part number TM21SS024A