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Shot put balls are typically made of lead and encased in a steel shell. Shot put balls can be made of solid iron or brass, as well; any metal not softer than brass is an acceptable shot put material. The ball must be spherical in shape and have a smooth surface.

【 在 l234567890 的大作中提到: 】
: 现在是不是也没必要是铅做的，毕竟铅有害
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FROM 116.233.223.*