And you can imagine once this little sliver is rotated, it forms, it forms, or you can imagine this length is the radius of a disk. And so, and just to imagine that, let me draw the entire disk. So if this is rotated around, if this is rotated around, it will become a disk. It will become a disk. It will become a disk that looks something like that. And I'll just call the depth of the disk, so the disk, if you imagine a coin, this is kind of the side of the coin, the depth of the coin, the depth of the coin right over there. I know I can draw that better than that.