"GP4" stands for "gear primary - 4 sets". Any metal-gear servo (made by any company) use a plastic primary gear - or set of gears - closest to the servo motor. This isolates the gear-train electrically, and also serves as a sacrifice gear (or gears) in a crash.

Sold Out but can be ordered

Notifications Notify me of stock updates to 4 sets Primary Gears for Hyperion DS20FMD,HMD,SMD,UMD