Inner diameter: 17.5mm This is a flat rim very similar to those of Tilz and Schmidt. Of the five rim width variations, ranging from narrow to wide, this is the narrowest model. For reference, the current new retail price is 12,100 yen (including tax). I used it only for a short time during a trial and after purchase. I washed it and stored it for several years, but I am selling it because I no longer use it. There are some minor wiping scratches and slight color unevenness that are barely noticeable. *The first photo appears to show color unevenness in the gold plating, but this is not actually the case. I was unable to photograph it properly with my smartphone. There are no issues with use, but please consider purchasing it with the understanding that it is a used item. Immediate purchase is welcome. Please refrain from excessive price reductions.