| 摘要 |
A curved, partial barrel shaped body has a bottom surface shaped to rest on a portion of a planar surface such as a pad or a floor and an upper curved surface formed by a first cylindrical surface portion having a first radius of curvature about a first axis and a second cylindrical surface portion having a second radius of curvature about a second axis spaced from and parallel to the first axis. The second radius is different from the first radius of curvature. The first and second surface portions preferably tangentially merge together to form a continuous smooth, curved, upper surface with different curvatures.
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