GPM MG321T/0.5M 40Cr Steel 21T Motor Gear for RC motors  [MG321T/0.5M]

This GPM MG321T/0.5M motor gear is a compact pinion designed for scale RC drivetrains that require a 21-tooth, 0.5mm module gearing. The part is listed as 40Cr steel with a hardened black surface treatment, intended to provide improved wear resistance and a longer service life compared with common untreated replacement gears.

Key measured dimensions are provided so you can confirm fitment: 21T tooth count, module 0.5mm, and motor tooth diameter 3.175mm with a round motor bore. The gear secures to the motor shaft using two 3x3 set screws; verify your motor shaft style and pinion spacing before installation to ensure proper mesh.

In practical tuning terms, this pinion is intended for straightforward replacement and light tuning work: matching module and tooth count keeps mesh geometry predictable, the hardened steel resists early wear under normal RC loads, and the round bore with dual set screws simplifies alignment on common motor shafts. Always check gear parameters and mesh clearance after fitting and before running.