These sleeves are a form of body strengthening and reduce movement of the vital chassis components. These are used on all Civic Cup cars as they reduce the need to reset the geometry between races. Why do you need them? During the production process the bolt holes in the bodyshell/subframe are made significantly larger than the bolt. This can cause issues due to the subframe being able to move around which is detrimental to the cars handling performance. The Honda Civic 07-11 also suffers from 'subframe click' - these collars eradicate the problem.