Invented 60 years ago by two engineers [Frank CotTER and G. Howlett DaVIS], this virtually indestructible drink ware is still manufactured in the USA. Made of a high quality polycarbonate [the same durable material found in airplane windows and space shuttles] that is ten times more impact-resistant than other plastics. They are virtually indestructible!
Even so, they come with a LIFETIME guarantee by the company.