Specially formulated Polunrethane Retrofit Kits designed for single axle variable rate suspension torque leaf spring suspensions on Class 6 & 7 vehicles, principally school bus vehicles. School bus fleets throughout the United States are presently utilizing these kits.  The bushing kits provide for increased control over suspension movement, which maintains alignment, improves handling, and extends tire life and fuel mileage. They provide for better vibration and noise control which improves ride quality and reduces wear on leaf spring and other suspension components. The specially formulated urethane is chemically resistant to grease, solvents, oils and other road elements.