The underfelt kit comprises the two main floor pan areas, a pair of felts to go under the front wheel arch carpets and a front bulkhead piece which should all be glued in place. It is cut to an outside shape but can be trimmed as necessary depending on the floor pan and tunnel arrangement of your car. The felt itself is dense enough to reduce a lot of drumming but flexible enough to be glued around the contours of the floor pan before the carpets are fitted on top.