Unlike other mouth guards (with a heavy spring) that tend to excessively extend the temporomandibular joint, the mouth guard designed by iM3 features a unique locking system that requires little force to hold the mouth in the desired open position inside the animal's mouth. The light weight of the guard and its spring, along with the unique locking system, help reduce the risk of myalgia, neuralgia, and/or trauma to the temporomandibular joint. There is an opening with a diameter of 8 cm.