Birthday flasks make perfect birthday gifts considering that a blind study conducted by the CDC in 2006 shows that 75% of the US population 21 years and older consume alcohol on occasion. The other 25% may not drink but the novelty of giving or receiving a hip flask is still there. That means 100% of Americans old enough to drink should give or receive a hip flask! A persons 21st birthday is the most notable when it comes to drinking so we have collected some really cool hip flasks designed around 21st and other birthdays. Having a birthday isn't the only reason to drink - anniversary flasks are popular as well!