The 'R' piston family consist of the Integra and Civic R pistons. Each of these pistons share a special 'moly' coating on their outer piston skirts for reduced friction. These 'R' pistons usually put out a higher compression ratio - depending on what engine you apply them to. The specs I have way below, are from stock compression ratios of the US and JDM 'R' engines.
The US 'R' piston has a lower dome than the JDM 'R' piston. Duhhh. Which means higher compression for the JDM version.
A nifty thing that I came across, when comparing these pistons, were the wrist pin oil holes. They're found on all of the 'R' pistons and GSR pistons only. Weird...I wonder why they didn't do that to the B16A piston family !?
Again, the part number stamped on the top of the piston tells you if it's JDM or not. The part number for the Integra-R pistons, is P73.