The finite wavelength instability generates trigger and packet waves in an extended three-variable Brusselatortype model. The trigger waves account for experimentally observed stacking (shock) structures and acceleration of oncoming waves before collision observed in the Belousov-Zhabotinsky system. Packet waves exhibit specular reflection from surfaces. The mouth of a narrow tube connected to a broader region acts as. a semitransparent mirror for packet waves leaving the tube, with a coefficient of transparency that depends on the tube radius.