| 摘要 |
As annular fitness ball has an annular body and an annular air-filled space that is placed inside the annular body. The annular body has an annular surface and a central hole is designed on the external side of the annular body. The cross-sectional diameter of the annular air-filled space must be larger than the cross-sectional diameter of the central hole. Protruding ears extend outwardly from opposite sides of the annular body. Pull strings extend through holes formed in the producing ears.
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