This is a 50 pack of Lung Bags for Prestan Professional CPR Manikins. With the Prestan Manikins you don't waste valuable training time fumbling with removable manikin parts, pistons or clips. Insertion of the one-piece lung bag design is a breeze! Fold it up, slide it in and you are ready for training. If students won't be sharing manikins during class, you do not need an additional manikin face shield.