Nytro - A-arm Thin/thick?

[yamanytroturbo]

Hi. I got a nytro rtx 09 and i just broke my lower right a arm. I found a used a-arm and im not sure what models its from, but the inner side where there holes for bolts looks pretty thick. Is there differences from these a arms?
What a arm does the 09 rtx use? thick? thanks.