This is what I told from BZM website.
CHROME PISTON RING 40 mm (50 cc)
zoom
RACING CHROME PISTON 40 mm - 50cc
zoom
The funny thing is that in BZM website, it stated racing chrome piston. Firstly, it is not a piston, secondly it is not chrome as shown in the picture. Also when I receive the racing ring, it state 018,004 so I presume it wouldbe for racing. I did post this topic on a euro forum. From the answer I get is chrome ring last longer, racing ring perform better because it teflon coated. I don't know. I am just stating the answer from the forum.