Bikini tube top
From Voyeurweb's Wiki about Sex
A bikini tube top is a small stretchy belt which covers her tits and is the upper part of a bikini. It has no shoulder straps or other means to hold it up. Typically a bikini tube top leaves a midriff allowing to see her cleavage. When worn while walking around, bikini tube tops swing up and down and left and right with her breasts. As illustrated below bikini tube tops reveal much more of the shape of her tits than a regular bikini top with straps.

