A stylish picnic tumbler or ‘glass’ adds to the sense of occasion. It needs to be strong, lightweight and packable so materials such as acrylic and glass-like polycarbonate are ideal. Designs such as the collapsible or ‘pop-up’ glass, employ a form of interference fit in which friction alone creates a join between two separate components. The use of this simple design technique creates space-saving drinking vessels, a valuable consideration in the picnic set.