Always replace in pairs, they fit perfectly in the back of my 2001 Volkswagen Beetle. The only thing that really worries me is that the boxes were different and one was not the same Manufacturer's name and there was no quality control, which made me suspicious. Otherwise they were identical, I put them on my car, I did notice a difference and ride quality due to the different shock absorbers on each side, but it wasn't too bad and they probably wear out pretty quickly because I live on a dirt road . . Not bad, not good, in the middle I would choose a little higher quality.