Allows diff angle change & subframe lock This kit is designed to change the inclination of the rear sub-frame while removing bush. The rings are used to preload the sub frame mounts removing the excessive compliance. By following the instructions & locating the rings in different planes it is also possible to induce rear squat (maximum traction) or anti-squat (drift) properties. This product is not designed for road use as it will increase NVH & should only be used with expert advice. It is however quite easy to install & remove the rings for weekend race meetings.