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The Kernel is a double jointed mouthpiece, the middle piece has been shaped to create a larger surface area on the tongue.
The Kernel is slightly softer than an Elliptical due to the shape of the middle piece. It creates a larger surface area and lifts the pressure off the tongue very slightly.
The Kernel is available in sweet iron. The Sweet Iron material was chosen as a metal option as it oxidizes. Oxidization encourages salivation and acceptance of the mouthpiece.