Sea To Summit Frontier Ultralight Collapsible CupBuilding on over a decade of experience in collapsible drinkware, the Frontier Collapsible Cup has been engineered to be sleeker, more ergonomic and lighter. Glass reinforced nylon 66 is used for the base, rim and center ring providing more stability and allowing you to grip the cup more easily. EU food grade silicone rubber sidewalls let the cup shrink down to less than 2cm in height. Designed to nest stack, these cups really do fit in anywhere