This is a 25 spline plastic servo saver from Kimbrough, designed to work with Futaba and Thunder Tiger servos. Kimbrough makes some of the best servo horns in the business, and their servo savers are second to none! If you have a high stress application where you do not have an existing servo save, you can use this servo saver to help save the gear of the servo during hard crashes. Great for steering applications on big monster trucks!