zero deck pistons?

I looked on the Summit site and it said "-6.20cc", although it DOES have a dome to it. It looks like the small perimeter of that piston top is the flat area, so that where I'd measure.

http://www.summitracing.com/parts/uem-kb399-030

cheers .yeh - not + that for 30 over mine 20 over so -6cc sposes that the dif.