Under Amour ArmourFit Mouthguard - Strapless. Under Armour ArmourFit Mouthguard is constructed of an ArmourFit material that molds to teeth for a tight; comfortable fit. Microwaveable; boilable and re-fittable. Provides a dentist-like fit; Under Armour's ArmourFit Mouthguard is chew resistant and makes it easy to breathe and talk. Microwave for 45 seconds or boil for 30 seconds then bite for custom fit. Hydrophobic material will not absorb water and will not deteriorate.