Precision steel micro-bearings. 
We think these balls are about 1/32-inch diameter. Ed Pegg reports that these particular balls were accidentally magnetized by noted physicist Stephen Wolfram, making them unsuitable for Ed's experiments. 
Source: New England Miniature Ball Corp 
Contributor: Ed Pegg Jr 
Acquired: 15 April, 2002 
Price: $5/1000 (which is not a lot of bearings) 
Size: 0.03" 
Purity: >95%
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