hi, i've to change both rear dampers on my sti III wagon, i can get them at 70gbp each for the black and 100gbp for the red. i think my car has the black ones but not sure cause it comes lowered from japan with -50mm springs.
also what are the differencies between black and red dampers? would both model fit on my car?

 

The standard ones were black on my STI 3, it was the later version 5 onwards cars that came with the red struts. They're uprated STI items.

Where is selling the red struts for £100?

 

have the black and red the same stiffness? can we fit the red ones instead the black?
you can buy them second hand at Jap performance Parts

 

The red ones are uprated and will be stiffer. Yes, you can replace the red ones for black, and the car should handle better.