The Leckey Mygo Dynamic Backrest Kit adds a cylinder to the seat/ backrest angle to allow for movement. This is a good option for children that have high extensor tone with extensor thrusting. Dynamic components absorb/diffuse the force of thrusting and provide assistance back to the starting seated position. Some users with sensory differences may engage in intentional rocking motions for input and calming. The Dynamic Backrest Kit will also be beneficial to them.