This is the small qingbai gaiwan I used. It weighs 120 gr with the saucer, 74 gr without. Its volume is 8.5 cl maximum and 6 cl normal. (It's made by a different factory as the singing cup, and the color is slightly lighter.) You will notice that the saucer isn't evenly round: it looks like 4 petals. Cute!
Its small size is good for travel or for solitary tastings. If the gaiwan isn't filled to the top, it's even possible to empty it in just 1 qingbai singing cup.
A gaiwan lets you taste the tea as it is. It's a great tool to study tea.