I bought 8L of pop, put it in my backpack, and carried it home. And it was HEAVY! But 8L is 8kg, and 8 kg can't be much more than 20 pounds, definitely less than 25 pounds. Twenty-five pounds isn't heavy! I certainly carried more than that around on a daily basis when I was in high school, and you don't just lose your lugging on your back muscles! So why did it feel so heavy?