The Battle Creek 523 is a reusable cold pack designed for general-purpose use. Here are the key features: Can be used alone or as a refill for the Ice It!® MaxCOMFORT™ System models 530, 540, or 550. Two 6" x 9" gel packs that stay flexible when fully frozen, molding around painful areas. Provides cooling therapy for up to the recommended maximum of 20 minutes. Durable and non-toxic, enclosed in vinyl material