Which additional damper used in rear shock?

[rogerkiu]

Hi all here! I need your help now. Recently I feel the rear shocks very stiff, so that makes my rear passengers feel really bouncing. I guess that it might be the additional dampers in the rear shocks have gone bad. I checked in realoem.com and found that there were two types of additional dampers used in the rear shock, in which one is 80cm and the other one is 90cm. Just wonder which type I should use if I am going to renew the additional dampers for my car.

Besides, do you have any other idea why my rear shocks run so stiff? Is there anything else gone wrong?

Thanks for help and your ideas!