Du-Bro Micro Adjustable Servo Arm Part No: 989. Fits Micro Servos with output shaft diameters from 0.152" (3.88mm) - 0.185" (4.70mm). Four arms included (2 with small dia. hole and 2 with larger dia. hole). Complete with washers, bolts and nuts. Made from 100% virgin glass-filled nylon for strength and durability.