Littmann Stethoscopes are available is a significant range of models and styles.

Here with some quick pointers -

Lightweight Series - Used for basic assessments, Blood Pressure (Because of the material performance expect a lighter sounds)

Classic Stethoscopes -  Considered by many as the industry standard.  The Littmann classics are can be used in general assessments. 

Cardiology Stethoscopes - Designed for optimal acoustic performance, these stethoscopes provide the greatest range of sounds and enhanced clarity over other models.

Master Stethoscopes - These are the best acoustic performers in their respective categories.  The single head helps to limit the ambient sounds.