AgAl2O3 materials may be packaged in a suitable flow-through reactor, close coupled to the exhaust manifold of a diesel engine, and upstream of other exhaust gas treatment devices, such as a diesel oxidation catalyst and a selective reduction catalyst for NOx. Preferably the maximum particle size is about 15 microns, the minimum particle size is about 5 microns and the D50 particle size is about 8-10 microns with the moisture content of the particle size \u201cengineered\u201d powder being less than about 0. The shoulder support includes a resonance chamber which is hollow for adding to the beauty of the sounds of the violin without detracting from the appearance of the violin during playing.