Is there a chart somewhere that compares the various grits for Siaair and Abralon.  For example, is using a 500 Siaair the same as using a 500 Abralon?

They both use the FEPA grading system. 500 grit Abralon - 500 grit Siaair. 4000 grit Abralon = 4000 grit Siaair, when both are new!! They use different chemical formulas for the abrasive so they wear at slightly different rates.

check out this grit chart

http://bowlingballexchange.com/attachment.php?attachmentid=964&d=1244342688