Aroma cup or fragrance smelling cup, as it's name implies, is distinguished by its cylindrical shape which is used to enhance and enjoy the fragrance of the tea.
Aroma cups are typically used only on the first steeping of oolong tea.
Pour the first infusion(washing the tea leaves and not for drinking) into the aroma cup through the tasting cup then pour the liquor away. Put the aroma cup close to the nose in a twist motion. The temperature of the tea liquor and the palm is enough to reveal the aroma of the tea which is further concentrated by the tall cylindrical shape cup wall.
Most aroma cups are made of porcelain and few are purple-clay cups with white glazed interior.