My DZ damper is worn out. I couldn't find a replacement so I bought another set. Obviously not a set of DZ. This kit is exactly the same as the DZ in looks but at half the price. So I bought two: one for each side. That works great. Whether a double kit is installed, I can not say. It doesn't open any slower and it's no harder to close. A double set is more appropriate in case one side fails unexpectedly. I recommend this kit over the DZ kit. It seems to be the same or better for half the price. Spirit.