From Team Associated:
The new #31662 inner arm mounts replace the stock machined aluminum mounts (#31619) with a machined brass version for increased mass. They are heavier than the aluminum version by 2.5 grams each.
A combination of these mounts, or completely replacing the stock mounts, helps with tuning the overall center of mass. Sold in pairs. The additional weight of the mounts is laser-etched.
Fits RC10TC6.2, RC10TC7, and RC10TC7.1.