Prepare your semi truck to be Ready for the Road Ahead , with the Velvac 3-1/2" Push / Pull Double Acting Air Cylinder that provides enhanced tailgate control. To control the movement of a pneumatic or hydraulic tailgate, this replacement cylinder pairs with an air compressor. Fashioned with rugged materials to be suitable for commercial vehicles, tractors, and more. FleetPride is your First Click in Heavy Duty .