I purchased the Adscope 615 after comparing reviews on Amazon and other sites. I also looked at the ADC website which compares the features with other ADC models and it lists the equivalent (or similar) model in the Littmann line for you to compare the features. I have some normal age-related hearing loss so for me, the clarity and volume of the Adscope 615 is a great improvement over the Adscope 603, and the Littmann Classic II for assessing blood pressure. I also like the oval shape of the diaphragm better. This stethoscope is a little heavier, but that is okay by me.