A:AnswerI went to google, no big deal.
MIPS (Multi-Directional Impact Protection System) aims to reduce rotational head acceleration caused by an oblique impact in order to further improve protection from rotational traumatic brain injury. So basically, MIPS is oriented towards reducing the rotation of your head by enabling sliding between the helmet and the head during any given impact.
A:AnswerThis is actually a good question... I ordered this Medium based on the sizing chart, but it sure seems more like it would fit a child's head. But, I think it is SUPPOSED to sit an adult head.