Speedrings and Ricta cored wheels aren't dual duro like these OJs, or the old ABs, or even the powerflex wheels (tho those are closest to the ricta chrome cores).
The ricta cores just have a hard bearing seat. whereas the speed rings are different in that they have an inner urethane ring that surrounds the bearing core, and then the ring, then the outer urethane (part you skate) so: bearing seat, urethane, ring, urethane.
From ricta, complete with typo:
"Ricta Speedrings’ unique core design puts urethane around the bearing bore like a non-cored wheel. You get the feel of a traditional wheel with the speed and reduced rolling resistance of a cored wheel. Less Rattle, More Roll"
I've skated speed rings a number of times and never felt an advantage in skating. Plus they only come in 95/99 now and the 99s were very grippy but felt harder.
The older chrome cores, before they switch to the NRG' branding were hard af and would rattle your teeth out.