For 2021, Beta is continuing to offer four two-stroke off-road RR models ranging from the agile 125 RR to the torquey 300 RR. There are two basic platforms offered—the 125 and 200, plus the 250 and 300.

The primary difference between the 2021 Beta 125 RR and the 200 RR is the displacement of the motor. Beta increases both the bore and stroke of the 125 to get it to a 200. That means more power everywhere for the 200, rather than focusing exclusively on more torque or more horsepower.
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https://ultimatemotorcycling.com/2020/05/28/2021-beta-rr-2-stroke-off-road-line-up-first-look/