The Riester Tristar® is a 3-in-1 stethocsope with three different sized double chest-pieces, one each for adults, children/babies and new-born children. It's the perfect tool for auscultation in all frequency ranges. It offers considerably improved acoustic performance in all areas of application.
I've been teaching auscultation for 45 years and this is the worst stethoscope I've ever tested. It really should not be sold