DuBro Tru-Spin Prop Propeller Balancer for Air & Heli - 499 Features: . Built for the modeler who expects the very best . Manufactured out of hardened material . Balances air props of all sizes and weights, boat props, spinners, car wheels, heli rotor heads, jet fans, fly wheels, more. . Securely centers and locks props on to the balancing shaft for utmost accuracy . Each balancer comes complete with easy-to-follow assembly and prop balancing instructions .