These are the DuBro Micro Adjustable Servo Arms. Fits micro servos with output shaft diameters from 0.152 - 0.185" (3.88 - 4.70mm) Made from 100% virgin glass-filled nylon for strength and durability Four Arms (two with small diameter holes and two with larger diameter holes Mounting Hardware Length: 1.3" (34mm) jxs 01/21/15 ir/jxs &