The RA Bock Single Head Cardiology Stethoscope with Tunable Diaphragm that responds with a simple pressure change to capture low and high-frequency sounds similar to the Littman models. Real World Review by me an ER Physician with 25 years experience: This is an excellent stethoscope choice if you are in the market for a Single Head Cardiology model similar to the Littman Master Cardiology. The Master Cardiology model is Littman's highest rated model on Amazon with a perfect 5 stars. It is also the most expensive model. If you have the money in my opinion you will never go wrong purchasing it. It was the model I choose to use most of my 25 year career. That said I feel our RA Bock Single Head model with a tunable diaphragm offers very similar function and is an excellent value for the price.