サーの称号が与えられた和牛の中で最も有名で最高級の部位。
牛の腰の上部、胸椎の後方部分のお肉。リブロースの後ろに続く部分です。脂肪と赤身とがバランスよく混じっていて、きめが細かく、甘み・風味に優れ、ジューシーな霜降りが多い部分です。和牛の中でも最高級と言われ、高級すき焼きなどで最も高価に提供されることが多いです。

The most famous and finest part of Wagyu beef, which is given the title of "Sir".
The meat is from the upper part of the cow's waist, behind the thoracic vertebrae. It is the part that follows behind the rib roast. It is a well-balanced mixture of fat and lean meat, with a fine texture, excellent sweetness and flavor, and juicy marbling.It is considered to be the highest grade of Wagyu beef and is often served at the most expensive price in high-class sukiyaki.