The flex carbon plate is designed for R8S chassis with the purpose to reduce the flex in the front suspension. When the flex was reduced, it will decrease steering and shaking in the front end of the chassis. The thicker plate makes less flex.
There are 2 different thickness options in the kit:
R818032 R8S Flex Plate 1.6mm (2)
R818033 R8S Flex Plate 2.0mm (2)