.3 ounce disposable plastic stethoscope head.
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. Discounts available in larger quantity (click here).