Replacement gear clutch for under the blade. It is only compatible with Nutribullet 600W 900W NB101S blades. 4 Gears are included. Worn out the motor rubber gears on your Bullet Blender? Blendin got the spare part for it. This set of four gears are compatible with Nutribullet 600W, 900W Blender Mixer Juicer. It is recommended to change the gears every three month for optimal performance.