I learned a little something new today.
The newer Rotax 185 pistons use L-shaped top ring. This top ring and the Rotax 377 top ring are the same (p/n: 215 210), but the bottom rings for those two engines are different.
The rectangular bottom ring on the newer pistons is the same as the rectangular rings used in both positions of the older pistons. The newer L-shaped rings are $40 a pop, don't bust them.