A device for treatment of exhaust gases includes a housing, a fragile structure resiliently mounted within the housing, and a non-intumescent mounting mat disposed in a gap between the housing and the fragile structure. The mounting mat includes a plurality of inorganic fibers that have undergone a surface treatment to increase the holding force performance of the mounting mat. Also disclosed are methods of making a mounting mat for an exhaust gas treatment device and for making an exhaust gas treatment device incorporating the mounting mat.