If you don't use a full face mask when playing airsoft, there are chances that your teeth might get hit by a BB which may lead to an expensive visit to the dentist. You might want to use teeth protection and here is a DIY made by Kasper Sundy that you might want to make for your own use... "Hey everyone! In this video I show you how I modified a clunky, uncomfortable mesh mask to a low profile, comfortable teeth protection. With this you'll never need to worry about getting hit by BBs in your teeth!"