6" wafer. 
Silicon wafers are the Gothic cathedrals of our age.  They are the most sophisticated, most beautiful, and most important physical objects created by human kind around the turn of the millennium.  They are created in huge numbers in sizes from 2" to 12", and most are cut up into individual chips.  A few defective ones are taken out of the line before that stage and sold in museum shops and on eBay, where I got this one and quite a few others. 
Source: eBay seller zeebidder 
Contributor: Theodore Gray 
Acquired: 11 July, 2003 
Text Updated: 29 January, 2009 
Price: $10 
Size: 6" 
Purity: >99.99999%
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