Are you still looking for a teaching apparatus to let your student know the acoustical principle? Then, our pronunciation gear is one of the best choices for you. Using high class material, it is safe and durable. A perfect physics teaching aid for you. It is a good helper for teachers, parents, train teachers, professors, researchers, etc. Features - Color: As shown. - Material: Iron. - Size: 8.00X8.00X0.50cm/3.14X3.14X0.20 inch. - Constructed by using high-grade material, ensures it safety and can use it with confidence. - Mainly used in middle school physics teaching, to explain acoustical principle. - Lightweight and portable, more convenient to store and carry. It's great equipment for students to learn the acoustical principle. - Let students learn acoustical principle in interesting experiments and improve their physics performance. - It is a good helper for teachers, parents, train teachers, professors, researchers, etc.