These Bushes are Genuine Mitsubishi Lancer Evolution Rear Diff Bushes. 
 
They fit all EVO models from EVO4-9 (EVO IV/V/VI/VII/VIII/IX)
 
Over years, all rear diff bushes start to worn, so when you shift gears quickly or suddenly accelerate the vehicle, the rear of the vehicle will make a big "Thumb" noise which is a typical noise / sign of Rear Diff bushes are gone.
 
We do not recommend to replace those rear diff bushes with Urethane Hard Bushes for Road Use Cars, because it will transfer a huge amount of unpleasant noise when you are driving. Therefore, to replace any worn rear diff bushes with Genuine Mitsubishi Rear Diff Bushes are suggested.
 
You could buy one or a set of 4 (Normally people will replace all 4 rear diff bushes at the same time to ensure that all bushes are in the same condition when driving)