Once again, please pardon my lack of 2-stroke familiarity but I'm wondering about piston rings.  When I dis-assembled my GT's 80cc, there was a flat segmented "expansion ring" (?) under the bottom ring.

The parts manual I have only shows the two conventional rings and likewise the service manual I have, speaks only of the two upper and lower conventional rings.

My new Yamaha OEM ring set, however, did come with the "expansion ring" if indeed that's what it's called.

Should this segmented "expansion ring" be installed under the bottom ring on a GT80/GTMX?

Thanks!  ZT