Many drummers cut a port hole into their bass drum resonant head. This provides an ideal place for a microphone to amplify your drum with, and it allows the air to escape from the drum when you strike it with a beater, which alters the sound of your bass drum a bit. It delivers less boom and more punch, which is often preferable in live situations where you need to be amplified and mixed through a PA system. However, cutting into it can negatively affect the integrity of the drumhead, as it can cause tearing. Luckily, Gibraltar has these Port Hole Protectors. Simply take the two parts, each on one side of the drumhead, and snap them together. This makes the area around the hole less fragile and ensures the material won't rip or tear.