Clarity: Clarity assesses the internal characteristics of the diamond as it formed in nature. This C factor is graded on a 10-grade scale and also impacts the diamond's rarity and value.
The fastest marathon ever was run by Geoffrey Mutai (2:03:02) at the Boston Marathon on April 18, 2011. But because the legendary Boston course does not meet IAAF layout standards, the World Record belongs to Patrick Makau (2:03:38) recorded at the Berlin Marathon on September 25, 2011.
In recognizing Kenyan Geoffrey Mutai's mark of 2:03:02 at the 2011 Boston Marathon as (at the time) the fastest Marathon ever run, the IAAF has noted: Due to the elevation drop and point-to-point measurements of the Boston course, performances [on that course] are not eligible for World record consideration..