Abstract: A releasably secured closure lid for potable containers having a perforated sectorial drinking section, the removal of which exposes inclined baffle walls. Potable waveforms generated by movement of the container impinge upon the baffle walls and rebound therefrom with reduced energy. The direction of rebound is toward the middle portion of the drinking section. The rebounding waves therefore converge upon each other from opposing directions and their individual kinetic energies are thereby dissipated by cancellation, thus reducing potable spillage.