Under Amour ArmourShield Mouthguard - Youth. Under Armour Armourshield Mouth Guard has patented Bite Flex and ArmourPlate technologies provide impact protection for teeth; jaws and gums. Under Armour Bite Flex absorbs energy on impact while contoured EVA material ensures a comfortable fit. Under Armour's patented polymer shrinks for a secure; locked in fit so the mouth guard stays snugly in place for easier breathing. It also makes it easier to talk with the guard in place.