A thickness figure needs a material breakdown. Shapton’s current FAQ distinguishes unbacked stones from its glass-backed construction, giving a buyer more useful information than a single overall number.
Technique and structure
RockStar is a 10 mm stone without a glass backing. The usual GlassStone construction combines a 5 mm stone with 5 mm tempered glass; product 50106 is an explicit exception, using a 10 mm stone and 5 mm glass. Equal overall dimensions therefore need not mean equal thicknesses of abrasive-bearing stone. The backing and the working material are separate parts of the specification.
The case is another specification
The FAQ describes Ha-no-Kuromaku as a 15 mm unbacked stone supplied with a plastic case. RockStar has a standard version without a case and a version with a stainless-steel storage case. Shapton also says the series have different grit line-ups; these dimensions do not establish equivalent grades or cutting performance.
For international readers
Read the exact product number, stone thickness, backing and included case together. This is a construction guide, not a hands-on comparison or a forecast of service life.
Global shipping and buying
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日本語
砥石の厚み：研磨層と裏打ち材を分けて読む
シャプトンのFAQは、RockStarを厚さ10mmの無垢の砥石、硝子砥石を通常5mmの砥石に5mmの強化ガラスを貼り合わせた構造と区別します。商品番号50106は10mmの砥石と5mmのガラスという例外です。刃の黒幕は15mmの無垢の砥石で、付属ケースも異なります。総厚だけを研磨層の量や切削性能と読み替えないための解説です。