The difference is that the Extreme Impact has added technology called shock pads built into the bottom of the mouthguard, and the Extreme Impact comes with a mouthguard case.The High Impact does not come with shock pads nor does it come with a mouthguard case. High Impact Mouthguards and Extreme Impact Mouthguards both come with sweet designs and both mouth guards are made from our most shock absorbing material Damprotech which has been tested in multiple studies to be more shock absorbent than the most common material used in mouth guards.