Which "drag race" master cylinder?

ok, so not to be the extreme cheapass, and i'm simply asking...not refuting the dr-diff...but whats the difference in that, and a $28 cordoba MC with the same specs?

http://www.ebay.com/itm/Brake-Maste...22-/161468350666?_trksid=p2141725.m3641.l6368

http://www.rockauto.com/catalog/moreinfo.php?pk=1370662

Bore Size, mainly. That one you posted is 1 1/32" The Dr. Diff that everyone loves is 15/16"