.3 ounce disposable plastic stethoscope head, set of 10.
This is especially useful if you're going out into the field and don't want to contaminate your 200 dollar stethoscope with hepatitis C! Get a bunch of these and don't worry about throwing them away when you use them. They work surprisingly well considering they weigh 3 tenths of an ounce and are made out of plastic.
NOTE: This is the HEAD ONLY. Also sold one at a time (click here).