Highballs are tall plastic glasses with straight sides. Strictly speaking, a Collins glass is slightly larger than a highball but this is a distinction that is only meaningful for professional bar tenders and cocktail mixologists.
In plastic, highballs stand out from tumblers because their shape is straight sided and cylindrical. This is a considered to be more stylish but comes at a premium because they do not stack, store, or transport as efficiently.
Nevertheless, their simplicity and contemporary looks make these plastic highballs a popular choice for premium and private events.