Provides a comfortable fit. Features a flexible frame with a pre-punched hole. Comes pre-assembled. For single-use only. Insti-Dam is designed to comfortably fit the outside of the patient's lips. The 1/2" offset pre-punched hole is made for easy positioning. With its built-in flexible and foldable frame, every single-use dam allows the taking of radiographs even without removal. Each pack comes in 20 conveniently pre-assembled dams.