Super Power Heavy Duty 650 KHz resonant 2" diameter x 0.219" thick DL-47 Piezoceramic transducer with 0.2" diameter center hole. This is brand new made for a Medical Company making Ultrasonic medical treatment devices by Del Piezo Specialties LLC. Even though these are new, they may have slight tarnish on one side of the Piezo (both sides are silver plated).