主体的下部中心设有圆锥形内孔，该内孔的头部为半球形。
The center of the lower part of the main body is equipped with a cone inner hole. The head of the inner hole is hemi-spherical.
主体的下部中心设有圆锥形内孔，该内孔的头部为半球形。
The center of the lower part of the main body is equipped with a cone inner hole. The head of the inner hole is hemi-spherical.
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