All mats are pre-cut and fit exactly in the planned position. It is not necessary to install all of them. Thus it is more important to achieve a balance of cooling and dampening, also depending on the hardware installed. The more heat is exposed from hardware the more openings and fans are needed for its cooling. Each case opening provides a way for the sound to reach the outside and there with be perceived as noise. Depending on how comprehensive the covering of the housing with dampening mats is, the quieter it is. There are three levels of dampening - the first should be installed in any case the second only if you dont use additional fans and very effective hardware is installed. The first stage includes the right side panel, front part of the left side panel, upper front, the whole floor, a part of the top cover and the middle part of the backside backside. Second stage would include the rear part of the left side panel, the middle and the lower front. In the last stage the fans in the top cover and the back are replaced by dampening mats. - Compatible with the Lian Li PC-A55 - Pre cut to size to dampen every part of your case - Self adhesive tape pre-applied