These specially made upper decks from flexible & durable glass fiber material increases the flex of the car and improves handling on low- to medium grip tracks.Machined from 1.5mm glass fiber material, the shape of the top deck has been specifically designed to achieve maximum traction and great steering characteristics at the same time.The top deck can be connected to the motor mount using these alternatives:1.) Soft setting - Only one rear screw is used. This allows maximum flex and provides maximum steering. However, the car is less stable on-power.2.) Stiff setting - Both screws are used. This setting gives reduced flex both in front and rear. Mid-corner steering is decreased, rotation is decreased. This setting provides maximum stability and makes the car easier to drive.